The one and only problem my mkiv 1.8 T suffered in the two years I have owned it was when it was difficult to start and ran rough when it did finally fire up. I took it to a local private VAG specialist just down the road from me -AG Brown.
He did the diagnostics and found the temp sensor to be at fault so replaced this, cleared the ECU fault codes and road tested it and all was sorted.
I recommend this guy to anyone in the Feltham / Hounslow area as he really knows his stuff as I understand he was a manager at a local VW main dealer for years before it closed and he now runs his own home based business.