Well, as for brands, you have 3 choices, Sony, Nikon and Canon, Sony is the least expensive of the 3, nikon tends to have good quality as with canon, I have 3 point and shoot sony's and a DSLR Alpha 350, you can check it's quality on my gallery with crappy lenses.
Places on the UK, have no idea... If you dare to eventually have some confusion, try pixmania, they have good prices, but sometimes "forget" to send the items.
Ebay on UK is also a very good spot and some regular stores also sell there, not only used, but also new boxed items, it's a matter of search.
The Nikon D40X, altough the one with lesser MP's, takes awesome shots, the Canon D500 may also be a good choice, its the one on the price range with greater MP (15), the sony goes 14.2 MP and the Nikon D40X goes to 10MP.
Remeber DSLR pixels have nothing to do with point and shoot pixels, the DSLR cameras have 1" CCD's whilst point and shoot don't go bigger than 1/4", also the lenses affect the picture quality, a point and shoot usually have 3 to 7mm lenses and DSLR use standard 35mm lenses, I'm waiting for some €€ for the Vario Sonar 60mm 1.1 for my Sony, pricey (1900€) but deserves, it's all made with high carbon crystal.
People don't like Sony cameras, however i've done a few photo runs against a Nikon D300 and an Canon 50D and they did took a beating from my Sony, must say that each one of these costs 3 times my Sony...
Now depends, if you want to have a substitute for a hammer to nail things to the wall, buy a nikon and pay the extra thoughness, not features, the canon tend to balance features (alot) and quality, the Sony is just that, a good no hammer like camera but costs ALOT less for almost the same build and picture quality.
Decisions, decisions, decisions