Turned out (we think as it's now working) that it was the cover on the
. This is located at the back of the engine bay behind the main engine block. It had worked itself a little loose and it ha rubbed the insulation off some of the wires going into it so there was copper showing. Got them insulated and it's now working fine and the
cover is well strapped down now. The AA guy who came to see it said he had seen it before...