You need a second opinion from some one else experienced who has a diagnosis computer to plug it into. As you said above mis diagnosis can cost money, but you've already cost yourself money with a mis diagnosis.
Didn't there used to be a directory of Vagcom owners on this site? Or was that on as VW forum somewhere?
There is also someone on this forum in the North East area who was fitting Dis and Cruise a while back, can't remember their username but if they ring any bells you could try them? or put up a wanted thread for someone in your region with a VAG computer?
Good luck what ever you do....