I would not be too fussed about an expensive router. If you can get a cheapish one that also includes a SPI firewall that would be good. Something cheap like this would do the job (USRobotics USR848004) -
http://www.broadbandbuyer.co.uk/Shop...ProductID=2421 . Cheap but includes firwall and 4 ports.
I have come across these similar problems sharing cable connections as the isp will only allocate one ip address per connect, hence having to use the router to share the address via nat. I used the USRobotics before with eConnect HomePlugs (85's)
http://www.econnecthomeplug.co.uk . As its got 4 Ethernet ports you can put a plug in one as well as have three spare ports should you want to connect anything else directly to it.