We recently purchased a motor mover which weighs about 40kg so we were a bit worried about the overall weight of our van as we have also got a spare wheel and carrier recently.
We took it to a public weighbridge with all the essential stuff we take away with us in it - minus clothing and food. I must say it was well worth doing as we now know exactly what extra we can put in the van and what has to go in the car. It is surprising how much the contents of the van weigh when you add them all up. The accuracy of the weighbridge is tested regularly by Trading Standards.
You can find your nearest weighbridge by googling it on the internet or phone your local council.