I think the best people to speak to are the mobile phone company with whom you have a contract with (be it Orange, Vodafone, O2, Virgin, T-Mobile, etc.) as they will be able to tell you what you need, what it will cost and probably give you some access numbers.
It may also be worthwhile to get in touch with NTL and see about picking up e-mails whilst away. They may also give you a dial-up number for use abroad.
As for the technology, you seem to have everything in order. One thing to make sure about is that the bluetooth on the Nokia will communicate with the laptop and the laptop can communicate with the modem (built into the Nokia) via the bluetooth.