I regularly get about 35 mpg average over a tank of V-Power from my DSG GTI, usually leave it in D but with the occasional foray into Manual :)
My commute is about 43/44 miles each way with about 30 miles on Dual Carriageway / Motorway and the rest on a nice twisty road...
Lowest I've seen on the commute was around 26-27 indicated after some spirited driving on the way home.... (MPG only ever suffers on the way home... can't think why...)
Don't really notice seasonal fluctuations too much...