I had it diagnosed at a local Audi “specialist “. They have all the VAG diagnostic equipment. They charged me 3 hours labour (£240) and said they wanted to order a module from Audi (£770+vat) to prove it then I could return the module and get a proven second hand one. Think they were just guessing. Unfortunately I’m back to square one and racking my brains for what the best next solution to try is.