Dear all
Having had problems with power under load and investigations by all manner of people, it turns out that the main stealer had not changed the DSG oil at 40k (or ever).
As my GTI had done over 100k by the time this was identified, I'm lucky that serious damage has not been done.
My power problems (subtle stuttering under load) was in 4th and 6th gears.
£150 for a DSG oil change - needs doing every 40k.