VW Polo - Electric boot release not working

I have a problem with SWMBO's Polo Twist 1.2 which has the optional remote central locking.

The hatch will not open using the handle which should trip the electric lock. The only way is to use the key.

Supplying Main dealer has had 4 attempts at repair under warranty, they say "that they replaced and resprayed the handle" Excellent job as they managed a perfect paint match and even replaced the dirt!! Interesting that they con their principal but that's another matter. It works for a few days after they try to repair it. Car is now out of warranty and they do not know what is wrong. After this dishonesty and inability to find the problem, I am reluctant to let them play about at my expense.

I have taken off hatch door trim and probed for 12v feed, nothing. I do not have a circuit diagram so would be grateful for colour code of feed. Possibly of broken wire but unlikely in 20,000 miles, I would have thought?

Has anyone any ideas?

Thanks
John