If the van is overweight it's overweight, insurance would be invalid should you have an accident, and if caught in the UK a hefty fine. The number of times you have travelled is irrelevant.

As you say this will give a headache to some of the boys coming over, piles of gear on the harbour side while they shuttle stuff up to the paddock!!

This check was nothing to do with the Steam Racket by the sound of it, however, in the past they have weighed vans BEFORE boarding, mine was weighed years ago before going on the old Vomit Comet, which I if I remember right had a 3.5 tonne weight limit.