7m limit - trying to chose our first van

Husband and I are looking for our first caravan.  We used to have a small campervan so know we want a 4 berth with fixed french bed.  Towing with a VW Touareg means weight is not an issue. So far so good.

Being boring and risk averse I've done so much research and reading my eyes occasionally feel like falling out and one of the things I learnt early on (thanks to this forum) is that the legal limit for towing in the UK is 7m.

But nearly every van we look at seems to be over 7m?  Are people deliberately or accidentally breaking the law or have I missed something?  If your outfit is not legal lengthwise what are the chances of an insurance company declining any claim in the event of an accident? 

Am I being over-cautious or particularly stupid?  Thank you in advance to anyone who can advise with this, and to anyone whose posts I've read over the last few weeks which have been so helpful