I think I've diagnosed my own problem...
I found this thread on here
http://www.cableforum.co.uk/board/11...ct-phones.html
The post by SMHarman suggests that DECT phones wont work if only 2 wires are hooked up - interestingly the engineer checked the cord I was using to connect to the phone and said " this cord should be fine as its using all 4 pins"....... So I popped the face plate of my NTE5 and there is only 2 wires..... Strangely I actually have 3 boxes and 2 cables. One it marked BT and has its own cable, the second is split between a Cable & Wireless box and a NTL box yet the engineer has plugged me into the C&W (yes, I've tried the NTL and that doesn't work)
Does this make sense as the cause of the problem?