Hi,
I had one of these back in 2003 and towed a elderly Elldis twin axle, which only weighed in around 1350 kg all in. Towed twice to the Med, fully loaded with roof box and bike on the back and 4 kids although the kids were fairly light back in those days.
Anyway, the car solo never ever saw 30 mpg on its onboard computer, and tank to tank refills driving across France it averaged 17mpg, which was horrendous, my brother following me on one trip, basically thought that something was up with the car because I kept pulling into pertol stations to fill up! On a performance front the car was fine solo, however would hunt up and down and mainly hold a lower gear hence even more fuel used, whilst towing.
I had the car for 2 years, and apart from the fuel it was faultless reliabilty wise, other than routine servicing. I eventually swapped it for a new Vw diesel Touran in 2005, which was way ahead in every department, towing at around 30mpg I still have it. These days I now tow with a VW Touareg, and manage around 20 mpg towing 1500kgs, with 3 bigs kids and 3 bikes on the back, and permanent 4 wheel drive, so expect the trade off.
Hope this helps.
Regards Paul.