All cordless phones that are compatible with the BT UK phone system will be compatible with NTL.
Other than that - any, really. I'd recommend going for a DECT (digital) phone, just because they're more secure (unless like us you like having your personal information being recieveable upto 300 metres from the house!!).
Argos/any high street store will probably be dearer than on the net. I've just had a look at a few places, and it seems all cordless phones are out of favour at the moment!
A few I've found though (not a huge help, nor was Kelkoo):
http://www.maplin.co.uk/search.aspx?...enu=y&doy=28m3