Thanks for the reply.
It was a person who is meant to be both gas safe and an inspector... It's a very old boat with next to no paperwork/history, etc. so nothing to invalidate. We just want it ready to live on as we've been working on it for over a year and a half and are getting impatient/despondent, so not too concerned about selling it on yet.
There was when we got it but everything was in such bad condition we decided to start again, so it would be from scratch.
We're in a marina, right on the outskirts of London. A van can get right close to the boat and could definitely be left unattended for the whole day. We've been quoted over twice as much and were wondering if that was regular.
I was thinking the same re the room-sealed but like Mike the Boilerman said there's nothing that actually prohibits them.
Thanks for the tip, I'll have a look.