You've done more miles than me (I've now only done 2600!). Things have improved slightly, but it's still pretty poor. Last tank averaged 35mpg, which I don't suppose is too bad - but a long, long way off what was advertised. The dealer I got the car from is now bust, so I took it in to another dealer for a check under warrenty and it "tested ok".... Which means I'm somewhat screwed, as they didn't want to know after that point. Because I can't go back to where I bought it from I might contact seat - but it's tricky as if everything is working ok, then they will just fob me off with "it's down to your driving".. The dealer did suggest to give it up to 10,000 miles to properly run in - but I think they just wanted rid of me, and didn't seem to know much about the 1.4tsi, and suggested it was about right.
I went on 60 mile run last week, mostly motorway and by sitting in 5/6th at 60mph I managed to get an average of 42mpg.. If you don't let the turbo kick in it's more efficient.. but I can't
help feeling a little peeved - I've drive diesels for years, and I've gone from a polo estate which averaged 60mpg+ on every tank (15 mpg above the book!), I chose the 1.4 tsi because I thought it would be cheaper to run - it costs me double!