You also have to consider that if the combined weight of your van and the trailer are 3,000kg i think it is and you did'nt pass your driving test until after June 1997 you cant legally tow a trailer with a commercial classed vehicle without passing the trailer test .
your right mate, it actually changed jan 97, I pasted my test in May 97, so I missed out.
I think, not 100% but we not allowed over 2.5 ton, may be less and can't tow trailers, for sure. We not allowed to drive a mini bus with 15 people on board only allowed 9 inc driver.
As far as those who can tow, or have upgraded three license, I don't see how it is illegal, it's just depends on where you leave it, and a good way of advertising.
I reckon a free clean for say, McDonald's or b&q or sutton, may get a blind eye turned to it being in there car park.