As mentioned by a previous poster, there are inaccuracies with the costumes in the film. The production seemed to focus on Janes apparent dislike of finery which was interesting, although we do know that Jane was not always clothed in dark colours. Some of the gowns date from a later period, like the gown she wears when she first speaks to Guildford in the garden. The gown Jane wore at the beginning of the film looked too simple for a woman of Janes rank. The wedding dress was odd; it looks like the costume designer wanted to go for the Spanish style but the headdress was weird and over-the-top. The gown itself was nice though. Overall the costumes were not that bad.
As for Janes apparent dislike of gaudy clothes, this idea is left to us by Janes tutor, John Aylmer. He recorded that once Jane received a gift from Mary Tudor (later Mary I) of wonderful material to which she reacted with dismay believing that such fabric was too sumptuous to wear. However what was modest by Janes standards is not necessarily what we would view as plain. Jane came from a prominent family closely related to the royal family, and as such would have had an array of jewels and expected to present herself in clothes that befitted her status to some degree.
Recently one historian has argued that this portrait:
http://www.somegreymatter.com/portrait2.htm
is of Jane and that the gown the sitter wears would have been viewed as slightly modest and sombre by contemporaries (when compared to the gaudy colours and sumptuous jewels other noblewomen wore). If this is what was known as modest clothing for a woman of Janes rank back then, then the gowns Jane wore in the movie are too plain and quite inappropriate for someone of her status.
Noli me tangere; for Caesar's I am

Hi Clare. Yes, there has been some objection to the costumes; apparently
the ornate finery worn by Jane's parents belongs to a later date, the
second half Elizabeth's reign rather than mid-16th century. I imagine
that Jane and others dressed themselves so dully because their religious
beliefs advocated starkl simplicity of dress. This was the style
that would be associated with Puritans just a few decades later.