I just acquired a 95 XJ6, nice car but the original Jaguar radio is driving me crazy. It will not turn off, I can't change volume or station, none of the buttons or controls work including the on/off button, and the station plays loud and obnoxious C&W. Apologies to C&W fans.
Here is a web address to a repair form for United Radio Repair. They repair Alpine equipment, which is who makes your radio. We've used them several times with good luck. Had trouble with one, but they made good on it immediately. Phone numbers are on the form, give them a call.