Just as an example:
On my Truck the plate states
GVW 2900kg
( max weight allowed when full of fuel & fully loaded inc driver & passenger's & kitchen sink )
GCW 5400kg
( this is the maximum total weight combination allowed inc trailer or caravan )
AXLE 1 1300kg
( if vosa stop me this is the max weight allowed on my front axle )
AXLE 2 1730kg
( & this is the max weight allowed on the rear axle ) but they both cannot be at the max weight or i will be overloaded
Hymer 530 ( 1600kg MTPLM ) inc 100kg nose weight
So when I go up to the local rollover weigh bridge with the sensor plates that the police & vosa use, my max total combined weight is always around 4250kg, I still have a safety margin of 250kg if needed, but only with this combination.......
The onus is on you to check the plate on your tug, do the sums, & go take it all to a weigh bridge or roll over one to check the weights as per axle, & write it down
But IMO this is the only safe way to check as it is the same way as VOSA will if you are stopped ......