The weight of the caravan at it base weight ( MRO = Mass in rolling order) is what to look at and provided you weigh everything you put in the van and it comes to less than 1200kg total you can tow it. The MTPLM is the maximum weight the caravan can be loaded to. Its a limit not a target.You are looking at a 4 berth with an MRO less than 1200kg. Unless ,like me and THO we have a grown up granddaughter who sleeps in her own tent, so a two berth for us. I have a caravan ( 2 berth coachman Amara which the MRO is 1030kg) , if the granddaughter was small then we would have installed a camp bed for her at the rear ( or me) or as a teenager, in the awning ( with lots of duvets), they need their space . An Elddis Xplore 304(circa 2001) circa which is a 4 berth ( rear bunk beds ) had a MTPLM of only 1050kg .so they are out there
I have a concern with measure every item approach.
Firstly the Mass in Running printed on the documentation, is not the value of the caravan you have. It was the value that a specific model of the caravan that was supplied for formal type approval testing. Due to manufacturing tolerance's, th e level of humidity and the mass of any factory fitted options your model has the actual MRO is likely to be greater than the value on the docs.
This is very important becasue if the caravan weighs anything over the printed value, the difference has to be offset by reducing the pay load capacity by the same amount.
By all means weigh everything you put in the caravan, and keep a spreadsheet, it can be illuminating, but there is a potential problem with using this method to work out your total pay load, because scales used may have rounding errors which accumulate with every small measurement make and cumulatively underestimate the real mass of the load in the caravan. It might alternatively over estimate the real mass, and You also have consider the scales absolute accuracy error.
If you stopped and found to be overloaded, there is no valid excuse. you are expected to account for any inaccuracies in the measurement systems you used to check the compliance of the trailer to its Gross Vehicle Weight limit.
The most important measurement should be done when the caravan and tow vehicle are loaded with people and belongings and none of the measured or calculated values exceeds any of the relevant load limits.