Well it's finally sorted.... After my turbo noise post I booked the S3 into the dealers as it wasn't running right, the power delivery was just not as it was before. After a few minutes my car was diagnosed with a broken camshaft sensor/belt. Apparently the ecu has identified this and shut the cams down into a sort of limp mode which has not given me the full power I was used to! The only down side is a £600 repair bill!!!! 4.5 hrs labour and £260 worth of parts. The engine makes a right vibrating noise when you start it which is apparently characteristic of this fault.