Hello David,
I admit I was being a bit provocative, but it seemed you are happy with your outfit so I did wonder what you were hoping for.
Lutz actually beat me to the answers, but I will add just one point; In your headline post you quoted Landrover as indicating kerbweights "from 1770kg" . This is perhaps a more accurate statement than many manufactures use.
However it does not by its self affect what the vehicle can tow. This determined by the vehicle manufacture and set out as part of the cars type approval.
It does affect how much payload the vehicle can carry, as the vehicles MAM cannot be violated. Obviously the greater the basic car weighs the smaller the loading margin becomes. And in the same way it does indirectly affect the available loading capacity for the maximum permitted train weight. - so that might affect the weight of caravan, that depends on how the individual manufactures set out their loading limits.
The only area where the 'Kerbweight' becomes a legal issue is with drivers who have only passed their basic Part B licence (Post 1st Jan 1997) Here the driver is limited to towing trailers whose MAM must not exceed the "Unladen Weight" of the towcar . The Govt' websites define ULW as
"The unladen weight of any vehicle is the vehicles own weight when not carrying any goods or burden. This is:
inclusive of the body and all parts which are necessary to or ordinarily used with the vehicle or trailer when working on a road exclusive of fuel and, in the case of an electrically powered vehicle, the batteries"
Technically this is not the Kerbweight, but as cars are not universally weighed, the simplest way of conforming to the regulations is to use the kerbweight figure (which will always be slightly lower than the ULW) when deciding what caravan to consider.
The other use of Kerbweight, is when producing the towing ratio. This is purely a calculation that never represents the true or actual relative weights of car and caravan. A car is never used or driven in its kerbweight condition, it will always be heavier than its KWt, the problem is you don't know how much heavier it really is, and it would be unique to that particular vehicle. So for convenience the KWt figure is used.
For similar reasons the real weight the caravan is not known, so again for convenience the MTPLM figure is used.
The resultant ratio (expressed as a percentage of the cars KBt) will be the worst case scenario. The actual ratio figure would always be better, by virtue of the extreme raw data used.
It is always sensible to choose the lightest caravan possible to meet your needs. By doing so you improve the chances the outfit will tow with the minimum of instability. And whilst that is the principal behind the infamous 85% guideline, it often used manner that suggests it has authority and guarantees a good tow; by its self, it does not. Good towing requires many more considered decisions than just the weight ratio.