Thanks Dan, I'm in Yorkshire, RPM near Harrogate have been looking after my car since I got it, previously had full OPC history. RPM have been praised/mentioned here before, they are ex Leeds JCT, and have looked after me well in the past - mind you they've had £7000, plus whatever this costs, out of me in 22 months so I must rank as one of their best customers!
Sam I did swop the radio cassette for a Nakamichi CD unit, which incidentally everyone is excellent and is very much in keeping/contemporary with the dashbord (no flashing LED's etc.), but this was 18 months ago. But the thought of the immobiliser crossed my mind although I'm not sure if it would merely stop the engine firing rather than stopping it cranking as is the case in this instance.