Apparently my car was hooked up to Seat diagnostics for a total of 16 hours and some of that time directly to Seat HQ in Milton Keynes. What it actually cost I don't know as it was done under warranty When I was handed the keys back it was running fine, but I wasn't told exactly what they had done. The suggestion made to me was that I need to drive the car further and harder to stop the carbon build up on the turbo charger. I suggested that I shouldn't have to drive my car further or harder, as when I bought the car no one at Seat said, this car is rubbish if you only do short journeys. Anyway I've solved the problem once and for all. Half an hour after getting the car back I part exchanged it for a Mazda 5. No more reliability problems for me.