Thanks Roger, but I think I'll pass on that idea.. Just doing this one was quite enough hassle! I'm ok with most stuff but electrickery isn't my forte.
yes Aldermog, it's a cut out.. I thought after looking at how the cars wired plus the small fire (read panic to cut power off! thankfully I'd left the battery terminal loose) it would be a good idea to have one.
One question though, it would make sense to use the isolator as another security device and take the key out when it's parked up. I don't intend to cut power while it's running (unless I need to!) , it would only be when turned off, so is there any reason why this might cause issue with the ECU etc?