Motorola V3im - £99 In the O2 Store, so if you're an O2 user or if you want a phone that has no branding stuck all over it for unlocking.
O2 seem to have the best bargin at present.
Buying a mobile is, as many people know like buying a car (a minefield of bargins, rip-offs and scams). I do all my own research into buying a moblie, checking out prices from all the retailers and coming to a conclution on a phone I personally like, for the best price possible.
You (if your on pay-as-you-go) always, always end up keeping your new phone for at least 2 years. So bear this in mind when you see a phone with a funny keypad or strange design (for example a phone the shape of a diamond), beacuse you may end up kicking yourself when you're skint and you hate your phone, the most used piece of technology you will buy.
Invest. For the reason of again, how long you will have your phone for.
Try before you buy. Grab a mate, or go into a shop and try out the phone/s you like, you may find that you hate the feel of the interface.
Have fun with buying a mobile, it sounds scary if you've had a bad experiance, but just geek-out with it and it'll be worth it when you get a phone you're happy with.