I dont know how it is in England , but if its anything like music shops in Canada ... Don't ....I will (as soon as i get the Chance) visit my local music shop to see what they can do for me.
You should find a luthier or shop specialized for violins, you will get better price and better quality instrument. And the pple there will actually know what they are talking about. You wont have a Jimmy Handrix wanna be as a sales man trying to sell ya anything. Let's face it, the violin is not a common instrument and most music shop dont have qualified personnel to evaluate or sell them.
Might be a good idea to go there with someone that can play and know a few things about violins too ... like your teacher ...
Atre.