... Be very interested in what the law has to say about mobile homes/caravans... but taken onboard about installing one in a house.
It doesn't matter whethere it's a towable or not, the definition talks about whether it can be moved. but there's a big difference depending on usage - whether occasional (AFAICT that means less than 28 days per year, a bit like camping in the woods) or not occasional.
Here's a helpful precis of how the regs apply in the Forest of Dean:
http://www.fdean.gov.uk/nqcontent.cfm?a_id=6430
I don't suppose it's a lot different elsewhere in England, and possibly even Wales, but the rest of the, er, Union might well be very different.
Quite apart from safe installation there are also air quality issues which are very local. For example where I am in Derbyshire a wood burner has to be certified to meet exhaust cleanliness criteria.
Building Inspectors exercise quite a bit of judgement. Once when I got planning permission for a boat shelter the planning department insisted that I get building regs approval too. I thought they were nuts. I called the Building Inspector, who took one look at it, said "It's not a building." and left.
Not overly chuffed at the £150 charge... it seems a little excessive, but if its the law, its the law. I don't agree with the excessive amounts people are charged in road tax for a diesel but its the law.
I look at it like this: right now I don't have to tramp around foreign countries with a quarter of a million of my countrymen looking for someone to take me and my young family in after some maniac, where I used to live, and for no particular reason, has bombed me out of my home. Ask any of the Syrians you meet what they think of a small charge to pay for a guy to check that the equipment in your home is safe for you to use.