There are two entirely different methods for delivering broadband - ADSL via the phone line and Cable from NTL or Telewest. The type of router you need depends which you have.
For ADSL you need a combined "Wireless Router & ADSL Modem" which replaces the USB modem generally supplied by ISPs.
For Cable you need a "stand-alone" Wireless Router, often described as a Cable/DSL Router (don't confuse the reference to DSL with the combined Router/Modems).
In general, models from any of the mainstream providers should be fine - Belkin, Netgear, Linksys, D-Link etc.