http://www.grandprixmodels.co.uk/
They seem quite popular, and have an online database that can be searched.
I agree with fly on Manchester, although I have 4 others within a 10 minute drive (all 5 are, in fact).
The closest is in Farnworth, but this concentrates mainly on R/C (has few plastic kits in stock; nothing new though), so I tend not to visit this one (even for my R/C stuff).
Next is Radcliffe Model Shop, which seems split 50/50 R/C Plastic.
Then there's Bolton Model Mart (who've been through a boom since I started *buying. They've just bought another shop closer to the town centre). They stock pretty much the same stuff as the one in Radcliffe; although, being closer to the town centre, they are a bit more expensive, and stock newer kits.
There's another one in Bolton, but it's one of those chainstore art/crafts/hobby type stores that stocks lots of Airfix kits, and very few (very expensive) Tamiya kits. Oddly, this was the first place to stock the 2000 Ferrari F1 kit out of those I've listed, but they seldom seem to get new kit in. (never seem to sell the ones they've got, either).
Lastly, there's Manchester. They have two floors. One is R/C, the other plastic; Probably the best of the bunch.
Only the town shops stock Tamiya paints though, which is a bind.
Since Beatties went down the pan, there's not as much choice. I remember buying 3 of Tamiya's latest models from the Leeds store 2 weeks before it closed for £8 each!
I tend to travel around the Northwest with my work, so I can usually find a model shop when I need one.
*note - buying, not building!
Regards
Mark