I currently have a 53 plate Grand Jeep Cherokee for towing. I previously had a Land Rover Freelander and then a Ford Kuga.
The Freeelander was awful in comparison and I wouldn't recommend. It just always felt like it was stretching it too much. The Kuga was ok (but a lot more than £5k), the wife loved it as it had all the toys and was only 4 years old, but I couldn't justify having that much money in a tow car and I never felt like I could just throw things in the back as it might wreck it.
The Jeep in terms of towing is the best of the three. I love it. It's a 2.7 CRD auto. It's like a big tonka toy and pulls and pulls - still gets me 30mpg when towing which is pretty good. They also have a lot of toys as standard. I got a 53 plate for less than £2k so I'm assuming you can get a much earlier model for your £5k.
I looked at a Land Cruiser but it was too big for the space we have, and I was advised the mpg was worse (not that you buy any of these for decent mpg lol). The Discos seemed to have a price tag for the brand and the early ones just seem to rot.