I've also got a Motorola, cost under 30 quid, but with a VGA camera so not as fancy as the one linked to by bran
I'd suggest checking the Carphone Warehouse and use their 'phone finder' option, as you can tick 'Bluetooth' and choose style (Flip, slide, candybar) and use PAYG under 'availability'.
Then it's down to your budget, network, and maybe a search in case Argos has it at a lower price. Also worth popping into Asda (as phone for 'Asda' are unlocked, so work on any network except Three). You didn't mention which network you use, and some phones simply aren't available on all...
The Motorola W377 is the one I have, but on T-Mobile (so I can use a Virgin Mobile SIM in it). The 4 cheapest flips work out at 35 to 55 quid by the time you've paid for a top-up on top of the phone.
Have to admit to being possibly interested in the sort of deal that gerontius linked to as Three is offering Skype for free on several of their phones.
I'm not currently using Skype, but it certainly has possibilities given so many already do use it, (and having it in a mobile makes it more attractive to me than being tied to a PC for speaking on Skype).