I live in Jersey so not much help!
If the instrument is for you and you're likely to reach a proficient level (grade 3? grade 5?) at least, then it'll be worth forking out that four or five hundred squids so you don't have to buy a better one in the next year or so! I'm about to spend around twice that on a viola for myself, which I expect to be playing in the local orchestra etc. I've been borrowing and yes, I'd like to have a better one, but I can't afford it what with the strings for my good fiddle... and the harp... and the flute... and the digital piano so I can practise at night... you know the drill!
You're best to go to a shop and try a few out though. The sound can vary a bit and you can also be sure that the instrument is set up correctly if you buy from a specialist violin shop. In terms of variation, my 'good' violin (music college standard) has a very deep sound, almost like a viola on the G, but doesn't have the sweet tones most people tend to expect from a classical violin sound. When I picked it out I was really into Bartok I guess! It's set up with Pirastro Oliv strings which actually accentuate that darkness, because I like it that way - other strings would have the opposite effect. Somewhere online there's a list of which strings sound like what to save you spending insane amounts of money experimenting.
Off the top of my head, Caswells are online but somewhere near Oxford, Bristol is violin-shop-central, there's somewhere off Regent Street in London and there used to be one in Winchester where I got my first fiddle but that was around 18 years ago. You can buy online from Caswells if you're sure you know what you want and they will set it up correctly - you can also ask to upgrade case/bow/strings etc.