Hello Andrew
With an MTPLM of 1750Kg it is a large caravan, and it is sensible to look for a vehicle that will out weigh it, but do not get too bogged down with 85%. The ratio de not have to equal it (as per Kevins posts), it is not that specific. And I do wish that people would refrain form using it as a target in isolation from all the other important factors that affect towability and control. You must also consider the way the caravan and car are loaded, The maintenance and repair of both vehicles, and the drivers abilities and driving style.
Even if you do 1200 towing miles, you are likely to be doing far more non-towing, so consider the comfort and economy of the daily usage over the towing needs. Wherever you have 4x4 you will be incurring higher running costs compared to an equivalent size of two-wheel drive vehicle. Not only poorer fuel consumption, but higher servicing costs, and in many cases higher VED based on CO2 products.
Most caravanners rarely encounter conditions where a 4x4 is the only solution; Traction matters can usually be avoided or overcome with a bit of forethought or lateral thinking or a bit of pushing from a friend or two!
In general the driving and passenger ride comfort is better in an MPV compared to a 4x4, and also road holding and safety are better.
For some people a 4x4 is the answer, but it is always a good idea to look for alternatives.