In reply to ChristineR:
We drive a van, proper van no seats or windows in rear. The key question (at least with Eurotunnel) is if you are using the van for carrying commercial goods, or just as a leisure vehicle. Commercial goods forces you to book through the freight terminal (more expensive, but greater ticket flexibility), where as with personal camping/climbing gear you can just travel with the cars and camper vans.
We have been verbally quizzed that there is nothing inside that 'we have been invoiced for' but never actually had a physical check, however one look inside would clearly show we are full of holiday stuff. In other words it's never been a problem.
Only used the ferry once, but again I think they needed us to confirm when booking that we were traveling for tourism and not carrying commercial goods.
Edit - ours is transit size and does NOT fit under the 1.8m height barriers.
Post edited at 21:33