WildGoose:
It’s easy to get confused, as everyone seems to be an expert when it comes to driving related advice.
The legislation is actually quite simple, just got to find the right place to read it from. Naturally, as proved by Working Time Directive legislation the source is always the best.
I assume you will have a category B+E on your licence. This allows you to drive a vehicle up to 3500kgs with a trailer.
If you have the B+E category, you need NOT be concerned with the 750kgs max trailer rule, that is purely for category B ONLY drivers.
The max trailer weight for category B+E should be determined by the towing vehicles manufacturing plate, this will give you the Maximum Train Weight allowed.
Allow me to use my own van for a quick example. 1995 Ford Transit SWB 120 (the 120 indicates the max payload of 1.2t in the case of the Transit range). The maximum gross weight of the vehicle is 2830kg, the maximum Train Weight is 3500kgs.
So this particular van, can tow a combination not exceeding 3500kgs, for example if the van was empty, kerb weight circa 1600kgs, it could tow a trailer of 1900kgs. If maximum payload was carried in the van, the maximum weight of trailer would be reduced to less than 700kgs.
The above is just an example of my own van. Larger vans will likely have a greater Maximum Train Weight.
If you go above a maximum authorised mass of 3500kgs with a vehicle and trailer combo for commercial use, a tacho will need to be fitted to the towing vehicle. Of this aspect, i’m not 100% sure on the details. I.e If you need it all the time, or only if using for hire or reward.
My interpretation of the EU rules is that if the vehicle or combination is under a maximum permissable mass of 7.5t and used for non-commercial carriage of goods, you are exempt from the EU drivers hours rules.
Concerning the specifics of trailers. Unbraked trailers can not exceed 750kgs, braked trailers can go up to 3500kgs. Most modern trailers will have a plate fitted to indicate maximum weights.
Hope this helps, fairly sure it is current and correct, but feel free to correct any mistakes.