At one of the Funster Rallies someone bought along 4 pads that you drive onto to get the weight of the van.I am not advocating breaking the law, but I bet for every 10 motorhomes checked for weight, 8 of them will more than likely be over the limit!
I'm sure someone on this forum can report back on the findings.
Bottom line is:
Next time you head off, fully loaded, go via the local tip.
Most local tips have weighbridges.
The cost is between free and £15.
Well worth the investment, even if only for peace of mind