David R,
Personally i would be looking at something around the 1900Kg mark with a towbar limit of about 100Kg to tow a van that size. This puts you in to the mid suv and large people carrier area unless you can run to a Merc, BMW or 300c.
There are people posting on here who would pull your van with Mondeo size cars and it's probably legal but I couldn't stand the stress of wondering if the clutch would take a standing start on a Porlock type slope or wether the rig would get off a wet field or climb a slippery incline from scratch;
and that's not to mention how a lighter car would get blown about towing in a gale or being buffeted by trucks and coaches.
My van is a mere 1500kg but I use an Automatic Shogun of about 2000kg to tug it and I never have a moments worry about the rigs capability to go anywhere in any conditions and that's how I like it.
Yes it does use a lot of fuel but I love my vanning so It's worth every penny!