Firstly thanks for your suggestions. An update of where we are at. I spoke to Audi Crawley on Monday and advised that the new bonnet switch didn't seem to make any difference and that "Karl Heinz", continued to chirp away after about 5 minutes when locked. Dealership was not interested in A2 clubs thoughts on what might be the problem.
Audi said that they would send out their mobile mechanic to me at home as the problem had not been fixed.
He duly arrived, right on time and spent some time on trying to make the fault happen, but low it would not. Karl's a stubborn b****r sometimes. He then plugged in his diagnostic kit and, hey, it registered fault with bonnet switch.
Audi man said, look see if the thing has righted itself, but if not, then could be a wiring issue in that area.
Mega bucks.
As I type, Karl's asleep in the garage, not a peep all afternoon.
To be continued, I think.