Thanks for all the replies everyone, whoever said it was right about Seat customer care, not even an aknowledgement of my email, wonder if thier complaints department is just like the Carlsberg one in the TV advert.
Anyhow, today I tried all the suggestions and tried using the cushions off the sofa which helped a lot and shows there is just not enough support in the seat.Or it could have been the pain killers I have been taking every three hours. Personally this is close to the best driving car I have had, quick enough to keep me happy, handles and grips like a car twice it's price and has so far returned 40 mpg on my daily 100 mile commute. I will get something out of Seat to get them to improve the seats.
Chris