Hi Chris,
I recently took out a contract with T-mobile, Flext 25 + Web'n'Walk, and it costs me 25+7.50. What are you getting for your extra £5? Insurance perhaps?
I had to do an 18-month contract, but the seperate insurance deal I took out allows me to terminate the contract after 6 months without penalty (I mean the phone contract). The phone is an N95, and I've come to realise that these things are no longer phones. They are handheld computers with onboard video camera, stills camera, MP3 player, Sat Nav units and so much more .... and you can make phone calls on them. Carphone warehouse did the deal for me - they're OK.
I haven't needed to use the phone as a modem for the laptop yet - my mooring has WiFi and I just use G3 on the phone when I'm out and about - otherwise, there are an increasing number of cafes and pubs and such which advertise free wireless broadband to drag the customers in and I just use those for the more wordy emails (and posts to this forum) that I want to write.
My advice would be to go to a Carphone Warehose outlet and talk to someone who knows what they're on about and strike a deal. The websites are fine if you want to find out your balance/make a payment/download ringtones ( ) but there's nothing like chatting to someone face-to-face to get what you really want.
Hope this helps.
JOTW