Hi, this isn't a silly thing at all, I wish more fantasy writers worried about how to describe place. It's so important. The reader has got to feel the world is real, because you're being asked to suspend disbelief with the magic.
For historical, there are some good reference books where you can get pictures of the clothes they wore in the day. I can't think of any off the top of my head, but if you got to the library they should direct you to something. Or if you are in London, perhaps go to somewhere like the Fashion museum
http://www.ftmlondon.org/ or the Victoria and Albert and they might have exhibitions on or be able to direct you to some good reference books.
Probably Emma D will know about historical source books (she writes hist fic). They will probably help with the fantasy too, since much fantasy draws on history for its sense of place and time.