If pulled in onto a weighbridge, and you are found to be over ANY of the limits pertaining to your outfit you will NOT be allowed to continue until your outfit complies.
Depending on how over weight you are you might get "Words of advice" or you might get reported for summons to a Magistrates court. Fines for overweight do tend to be pretty punitive!
If your unit cannot be configured to be within its limits by moving stuff around that can then result in equipment being removed from the outfit. The Police VOSA etc have no requirement to ensure the safety of anything so removed, so it could just end up being left at the weighbridge, its security remains yiur responsibility at all times. (yes I have seen that happen more than once) Once the outfit is legal you will be permitted to continue on your way.
Don't underestimate the seriousness of being overweight. Not only can it be dangerous, but it can also work out to be very expensive in regards to fines. So it pays to know what your unit weighs at all times.
There is little point in carrying a weight ticket with you as, like an MOT its only valid/relevant at the time it was weighed. The ONLY thing that matters is what the weighbridge shows when your outfit is placed upon it. Don't forget any passengers etc will be required to remain in the vehicle during the weighing process. In addition dont lose sight of the fact that water weighs 1kg per litre, so a full aqua roll weighs 40kg+ (do you have an onboard fresh water tank with water in it??
If in doubt drain down everything prior to venturing onto the road.