Hi Nigel, be carefull with Subaru's as they are very thirsty, we had an Impreza Turbo [1998] which was an excellent towcar but quite light at around 1250kg, we towed an old Elddis which was 1000kg loaded and only it did 13mpg towing and 18mpg solo. The Forester is a little heavier at 1345-1435kg [2001 models] and in non turbo form a little more economical but not much as being less powerful it will have to work harder with a caravan on the back. With four wheel drive and a large boot the Forester is a good alternative to normal 4x4s and they drive like a car rather than a boat like some 4x4s do but your caravan maybe too heavy for it. I had no regrets buying my Impreza as it towed well and never ran out of power, it was lots of fun on its own and I knew it would like a drink before I bought it but be aware they are expensive to run.
Simon.