The scenes before at the beginning of in Episode 4 of the meeting with Axel are shot in the market square of Retz in niederoesterreich Austria close to the Czechia border. The market square is easily identifiable by the two large fountains that are show cased in the shot as Pym he drives in with the old skoda. The market square itself is famous as the second largest in niederorsterreich after Linz and third largest in all of Austria and the kilometers of underground wine cellars

The scenes by the seaside were indeed filmed in Dawlish. In fact that piece of railway was infamously washed away in the winter storms a few years ago!
Looking at other locations used, does anyone know where the scenes set in Czechoslovaia were filmed? I realise it looks very "eastern European" but I doubt the Czech authorities would have allowed filming! The cars used in those scenes (a coule of early Skoda Octavias, a Trabant and a Tatra) are all brilliant! As to locations, the usual sources don't have much information, hence the inquiry.

It is Dawlish, Devon in the UK.
You can easliy find the row of guesthouses on Google Earth. Just follow Marine Parade adjacent to the railway. It all looks a lot brighter and spruce now.