a phone like the Sony E T610 (free with £25 a month sub & cashback from some places) + a bluetooth enabled PDA (£200 ish)- Orange do a service for £4 a month that will let you get a moderate amount of surfing (3mb). this service doesn't eefect your free minutes
You could just download Opera Browser for any of the current smartphones (7650,3650. 3660, 6600, P800, P900 and SX1) which would allow you access to the internet @ GPRS connection and also resizes the web page to fit youir screen.
I have a moto mpx200, has full pop3 email and internet access. Internet explorer is as good a your going to get on a mobile, some pages don't resize which is a pain, web pages with frames won't work. If you just want to do normal browsing then its fine.
I've heard that the Sony P900 with the Oprea browser is supposed to be the dogs, much easier to surf with as well. It depends on weather your going to put form over function.