I was in birmingham a few weeks ago, visiting my best mate, and we stumbled across 3! it made me laugh so much... i mean birmingham is about as far away from any beach as possible. There's a billabong (which is mainly fashion) in the bullring, and 2 almost next to each other on the same side of the main shopping street (?corporation rd - the one where argos is, but further down?) - one is o'neil and it's massive on two floors - it's got loads of stuff in there. I'm sure they'll be really helpful. Or you could wait till you get a few lessons in newquay (if you decide to go). There'll be a better choice and second hand boards to choose from.
PS. I'm sure someone else will say this too, but when you're learning you need a big board (unless you have fantastic balancing skills). A short board may be practical to carry, but it'll take you years to stand up on it and you'll probably get really frustrated. I got a 7'2 and it took me AGES
I think you'd have much more fun learning the basics on something over 8ft. Perhaps try renting a few different sized boards so you get the feel of it before you buy something.