radio fault

I already had an aftermarket Kenwood radio installed on my 05 Treg, reception was poor so I got a new one. Took it out, tested the new one which did not work but is a working radio, then reconnected the Kenwood and that does not work now. No power to it. I called for some advise and was told...

Hi All, My radio/cd has developed weird a fault - the stations re-tune themselves and I can't turn the radio off, even when I turn off the ignition? The fault comes and goes with periods of normal followed by periods when there's no control at all? I have been quoted £800 for a replacement unit...