Look at diesel MPV's from Ford VW or Seat, about 28-30mpg towing your Lunar and 40-45mpg solo. go for at least a 130hp engine, they may not be the most dynamic looking vehicle but MPV's offer the best combination of carrying capacity, economy and stability.
7 seat MPV's are designed to be stable at high speed carring a relatively high load and make very stable towcars, their achilles heel is front wheel drive traction (lack of it) but we will use snowchains when we get bogged down but so far have never been stuck towing a twin axle with a Sharan and a ford S-max.
An interesting option could be a Ford s-max 2.5 turbo converted to lpg, serious fun to drive and similar costs to the 2.0 diesel.
Currently we tow a Lunar Lexon 640 twin axle 1266/1600kg with a 2.0 S-max tdci which is very stable, I've pushed it as far as I dare without getting it to snake, it is virtually oblivious to crosswinds and passing HGV's but being front wheel drive you need a gentle foot on the grass and you can't give it full right boot at junctions.
If you would like a more economical four wheel drive, look at the 4wd saloons/estates from Audi, VW, Volvo or Jaguar