When I get home I'll see whether there are any part numbers on the invoice when they repaired mine if that helps them locate where it might be (assuming that my dealer replaced the right part too!), they said something about changing an oil feed pipe, one other pipe and some seals. I've now done nearly 700 miles since they changed it and no sign of the leak returning. Strangely enough, they did pre-order a new turbo in for the oil leak and then decided not to change it.
Either way, hope you get your leak sorted once and for all. I think we all share in your frustration - if this is a common fault you'd expect VW and the dealers to be sharing information to take away the guess work, frustration and cost of repeat visits.