Dear all,
I have managed to sort out the problem and will describe what happened so that others may learn from my stupidity.
The issue didn't start until I tuned in the reciever on the BM5000 when I purchased the system there was a coax cable plugged in which I assumed was for the radio airial. I plugged this into an old portable TV airial and waved it arround to find the best signal. I live in a dip and reception is poor. The best signal was recieved when I rested the airial ontop of my CX100 speakers.
The case of the speaker is aluminium, so I think I created a circuit which caused the formentioned problem. Anyway I have removed the airial and all systems are back to normal. Thankfully the BM 5000 is robust enough to withstand my stupidity even after 20 odd years.
Does anyone know the correct airiel to use and where I could get one??
Cheers Nick
P.S. thanks for the advice, it made me call a local hi fi repairer who told me the problem could be in the speakers which put me on the right line. All for free.