I wouldn't upset the apple cart too much mate, just ensure you provide the correct oil for future servicing for peace of mind. Their customer care seems better than SEAT's so i'd keep them sweet and maybe pop in with a "thankyou" slab of beer? Saved you alot of hassle and possibly some money, so its a cheap way of showing your appreciation.
Sounds like a bloody good garage! The crate of beer sounds like a fine idea......
Just don't get a mad rush to your head if you get an urge to floor it with a new turbo fitted.
Give it plenty time to settle down and it will repay you in the long run.