adamss24 you were right! Turbo is red herring
Hi adamss24 and all the other contributors to thread "Turbo Wastegate "Stuck"" and many thanks to you for your help. Adam and others were correct that the turbo story is twaddle, there is no overboost and the Multitronic or its controls are at fault.
Also thanks to this forum for suggesting Colin Hicks, Independant VW /Audi Technician covering Yorkshire who was very helpful and knowledgable.
I will shortly tackle the Audi main dealer over their incorrect diagnosis and will let you know how I get on.