puppymalo, it might be worth trying out some different phones/brands to find one that works with your exchange using Argos' 16-day money-back guarantee.
I am using the Binatone MD1000 (which has a headset included) on my NTL line in Cambridge and Caller ID works (but as I said elsewhere this will not mean it will definately work on your exchange as well):
http://www.argos.co.uk/webapp/wcs/st...roductId=85667