VW Passat 1.9 TDi PD130 - towed my dolly and MK4 Escort all the way from Dorset to London and averaged 38MPG as I wasn't hanging around much either.

Have used it to tow a two berth caravan (have a compass lynx) without any issues what so ever.

If you're going to go for a passat, make sure you get the PD engine type.