I have a BT Studio 3500 twin set, and the handset on the base set has developed dreadful "white noise". I am not able to use the handset to receive or make calls, but the ansaphone etc. still works fine. I am able to make and receive calls on the base 2 handset. Is it a fault with the base unit or handset? any suggestions re rectifying the problem

Geoff Greenwood, July 2011