it doesn't really matter much to the rest of us who are part of a global audience though.

on your planet do they forbid people from moving to other towns?
http://www.hesaidshesaidreviewsite.com/

The lengths people will go to for an explanation
My goodness, you do take yourself just a little too seriously.

That incarnation of The Doctor decided to stay true to his roots. Perhaps the others were a bit on the aspirational or pretentious side.
The lengths people will go to for an explanation
Ecclestone did an RP voice in 28DL, so I wonder if there was a reason for him not doing the same in DW or whether it just didn't occur to anyone that the accent was different to that of previous Doctors.

That incarnation of The Doctor decided to stay true to his roots. Perhaps the others were a bit on the aspirational or pretentious side.
The Time Lords are falling down on the job: they can change everything, including clothes (I think they change, or does The Doctor have a bit of a scratch around The Tardis until he finds something that strikes his fancy - can't remember?) about the doctor, except his/her sex (thinking here of Romana - although I vaguely remember her turning into something completely alien, so who knows what sex that was - probably wrong here) and the origin of his accent. Bit sloppy! Don't the inhabitants of Gallifrey realise that the devil's in the details?
Maybe Christopher Eccleston's Doctor didn't have time to squeeze in a quick course at drama school, to polish up his Received Pronunciation.

It's never been made wholly clear what can and can't change through a regeneration, but some things did stay the same - his gender at least, and his accent has generally been RP(ish); even David Tennant (a Scot) followed that. Ecclestone's accent is a bit of a sore thumb.
And the remark 'other planets have a north' makes the problem clearer, because if the Doctor is a 'northerner' then why didn't the previous incarnations have northern accents too?

His doing so in DW created a bit of a continuity problem, as (AFAIK) no Doctor before or after had a northern accent.
So? William Hartnell, the first doctor, portrayed him as a 70ish grandfather. Jon Pertwee had grey/silver hair. Tom Baker had curly brown hair. Peter Davison was in his late 20s.
And you think that Christopher Eccleston's accent provided continuity problems!

Have you BEEN to London? It's crawling with Irish people. His parents are Irish, too, though perhaps it's a bit odd that they had all moved over to London (at an age where Jim was presumably old enough to still retain a strong accent) - it may have been more realistic if he'd said at one point that his parents were still in Ireland, though that would have cut out the tragic subplot where he discovered the bodies.
I haven't met any Irish on any trip to London, though of course I haven't exactly met the whole population.
It's not that he's Irish or has an Irish accent at all that I find odd. It's the fact that it's never commented on by him or any other character, not even in passing. Also, the notion that he's just visiting London or had recently moved there is made very unlikely by his parents living there too.
It's also interesting that another member of the cast, Brendan Gleeson, is also Irish but affected a decent cockney accent. Wonder why Cillian Murphy didn't do the same.
I think Hannah's garbled accent was merely because she was a terrible actress - often she sounded Australian.
I agree her acting was terrible, but surely she could at least get an accent right.
Not sure why Chris Eccleston didn't get to keep his northern accent, considering he kept it when he played the sodding Doctor ('lots of planets have a north').
His doing so in DW created a bit of a continuity problem, as (AFAIK) no Doctor before or after had a northern accent.
In a sad way it might have been because it was more convincing for him to be a man with great superiority and authority if he had a 'posh' accent.
He also has a rather posh name ('Henry West').

Have you BEEN to London? It's crawling with Irish people. His parents are Irish, too, though perhaps it's a bit odd that they had all moved over to London (at an age where Jim was presumably old enough to still retain a strong accent) - it may have been more realistic if he'd said at one point that his parents were still in Ireland, though that would have cut out the tragic subplot where he discovered the bodies.
I think Hannah's garbled accent was merely because she was a terrible actress - often she sounded Australian. Not sure why Chris Eccleston didn't get to keep his northern accent, considering he kept it when he played the sodding Doctor ('lots of planets have a north'). In a sad way it might have been because it was more convincing for him to be a man with great superiority and authority if he had a 'posh' accent. Probably not something they would have paid much attention to if they made it today.

It's a lot more realistic that this was never explained
If it had been explained, I wouldn't have made this topic.
perfectly reasonable to think that he grew up in Ireland and moved
back
to the UK at a later time
What makes you think he was from the United Kingdom originally?
Really quite glad, in fact, that the film didn't waste time explaining this because it had little to no relevance to the plot.
If it had no relevance, why include it to begin with?
As I once heard a TV writer once put it, it's better to be in the dark about something than have every little detail spelled out to you.
I just find that confusing.

Absolutely correct. Real life also lacks a 200 piece symphony score. Which is too bad because the music could warn us when something bad is going to happen.

It's a lot more realistic that this was never explained, and perfectly reasonable to think that he grew up in Ireland and moved back to the UK at a later time. All kinds of possibilities. Really quite glad, in fact, that the film didn't waste time explaining this because it had little to no relevance to the plot. As I once heard a TV writer once put it, it's better to be in the dark about something than have every little detail spelled out to you. Real life doesn't always offer explanations, and a film shouldn't always either if it wants to seem natural.

Largely due to immigration from outside Britain, not people moving there from elsewhere in the country.
This is false, more people come to London from else where in the UK than they do from overseas. It's a close run thing but internal migration is the majority.
https://www.theguardian.com/uk-news/davehillblog/2013/oct/27/london-population-changes-june-2012

I spent fourteen years in the U.S. Army. My last duty station ,before I separated in 2000, was at Fort Drum (home of the 10th Mountain Division) which is way up in northern New York state. In my unit on any given day you would have found soldiers from U.S. Virgin Islands, Puerto Rico, Guam, all fifty states, Canada (yes foreign nationals can serve in the U.S. military), Guatemala, Germany and South Korea (and those were just the ones that I knew personally). I whole bunch of different accents to say the least.
I now live in a moderate sized city in southwestern Idaho. Here you will find folks from the southeastern United States (typically referred to as "The South", Australia, Hawaii, Alaska, Massachusetts (in particular the Boston area), New Jersey, Malaysia, Mexico, India, Vietnam, Canada, Ireland so on and so forth. And we're considered a backwater of the United States by many.
I would imagine it's pretty much the same in England.

Only about 40% of people living in London were actually born in london.
Largely due to immigration from outside Britain, not people moving there from elsewhere in the country.
As for the army, units are not put together by the soldiers city of birth you could have one unit with people from dozens of different cities from Wales, Scotland, England, northern Ireland or any commonwealth country.
I just find it odd that a group so far north nearly all sound so southern.

Only about 40% of people living in London were actually born in london. As for the army, units are not put together by the soldiers city of birth you could have one unit with people from dozens of different cities from Wales, Scotland, England, northern Ireland or any commonwealth country.

For beep sake!

Don't people in the UK move around?
Maybe Jim is Irish and moved to London for a job opportunity.
I legitimately laughed out loud at that.
http://www.hesaidshesaidreviewsite.com/

Interesting, I'll have to study this bit next time I see the film.

Actually you are wrong there.
When he is in his house he is watching a video tape of his parents, just before an infected hears the noise and crashes through the window.
In the video his Dad speaks with an Irish accent and his Mum speaks with an English one.

do you not remember his parents (dad in particular) were also Irish, surely that explains his accent.
I don't remember his parents speaking in the film, or their nationalities being made clear. IIRC their bodies are found at their house and Jim or one of the others reads out a brief note they left behind for him, then the film moves on and nothing more about them is said. So almost no specific information about them.
Not only that, but why does his accent need explaining at all, London has (probably) someone from every nation on the planet. So what, an irishman survived the end of days, whats the big deal with that?
If a film was set in Moscow and the main character had a French accent, wouldn't you find that a bit odd?
And Jim is never specified as an Irishman, he just has an Irish accent which is never explained in any way.
The soldiers, being based in manchester again is feasible, soldiers come from all areas, and are based in all areas. The main soldier, ricky hartnett, was a cockney, chris ecclstone was northern posh, the sargeant was a scotsman, whats that got to do with anything? Are you suggesting that the army can only recruit and deploy people from the same areas with the same accent?
I thought it was odd that soldiers would have accents from other places and not the place they were actually in.

are you guys serious??? do you not remember his parents (dad in particular) were also Irish, surely that explains his accent. Not only that, but why does his accent need explaining at all, London has (probably) someone from every nation on the planet. So what, an irishman survived the end of days, whats the big deal with that? Given the make up of London, surely the focus here should be that out of all the survivors in London, theres three white men, two women (one who's black) and not a single asian - SHOCKING!
The soldiers, being based in manchester again is feasible, soldiers come from all areas, and are based in all areas. The main soldier, ricky hartnett, was a cockney, chris ecclstone was northern posh, the sargeant was a scotsman, whats that got to do with anything? Are you suggesting that the army can only recruit and deploy people from the same areas with the same accent? if thats the case lets just recruit millwall and chelsea fans and send them into syria, that'd shut the isis brigade up.
Such a bizarre thing to post about.

It matters if a movie is trying to be realistic.
I'm going to assume you're not from or familiar with the UK if the accents didn't stand out as different to you.

Does it matter?
I never noticed any different accents outside of the UK accent (since it is a UK film duh).