I'll give you the horsebox, but a dinghy is fine behind a Mini. I know, I've done it. And I mean a real Mini, not the modern BMW thing.
I don't reckon a Dart cat (130Kg) or a Laser (59Kg) even with another hundred or so for the trailer, needs 4wd.
Ron's snow is a real reason for having one. He seems to be one of the few people with a proper reason.
Ron,
I suggest you rent a decent modern road car one day for the Shropshire trip, just to see the difference. Preferably just so you can do a (practice) emergency stop on a wet road.
Andy