I've replaced the central locking motor twice but the same problem occurs - when driving along if I lock the doors from the inside they will after a period of time unlock themselves. When the car is parked, if I lock the doors after a period of time it will unlock itself, and occasionally it was winding the windows right down as well!
You can hear the central locking motor 'pulsing' in the boot, and the interior courtesy lights will come on and off.

Has anyone seen this before and can offer advice? I'd be most grateful!

It is probably some control unit/chip somewhere. I had my car relocking itself when I had unlocked the whole thing via the trunk key. It was weird - but after a month of doing this it suddenly started working properly.

I would talk to Audi about it and see what they suggest...