Just to chuck my 10p worth in on this. As far as I can determine the caravan's Maximum Technically Permitted Laden Mass (MTPLM) must not be greater than the towing car's Maximum Permissible Towing Mass (MPTW) defined by the car manufacturer and the combined actual laden weight of the car and caravan must not exceed the Gross Train Weight (GTW) – the maximum permitted weight of car and caravan together specified by the car maker. (Source: Towing advice - The AA).
Also found "The Camping and Caravanning Club, like many others in the industry, recommends you only tow a caravan that weighs 85 per cent or less of your car’s kerbweight. Those who are experienced at towing may go up to 100 per cent of the car’s kerbweight, but no-one should tow a caravan that is heavier than the towing limit of the vehicle it’s behind. Legally, if you add together the Maximum Authorised Mass (MAM) of your car and the MTPLM of your caravan, the total weight must not exceed the GTW of the car."
So to my mind you shouldn't exceed the towing vehicle's plated towing limit with the plated max weight of the van or the plated gross train weight of the vehicle for the outfit.
Well at the moment 25 weekend rallies (running two of them), 2 weeks in France in July, Spring Bank holiday visit to Sandringham, Christmas somewhere in the van and probably another rally somewhere at New Year.
Used to rally here many years ago with the Elddis Owners Club. There were no hard standings in the first field at that time and I remember the owner (Wally?) driving round the site first thing in the morning with his small tractor and trailer collecting all the children to go feed the animals.
I also remember breaking down there once in the old Discovery when a CV joint failed just as I pulled into the field!! Happy days.