Christian McArdle wrote:

Would I be breaking any regulations and/or should the building
inspector be involved ?


I would be very surprised if it is legal. The building regulations are very
strict about the safety controls of these devices. In the rest of the world,
where they've been used for decades, the regulations are much more lax,
although I suppose there could be a European trade directive saying that if
they're legal in France, they have to be accepted here.


Do I have to fit a vent pipe (think I do)?


That would make it an unpressurised cylinder and, therefore, would almost
certainly make it legal, but it would require a header tank and not provide
mains hot water.

Er. not so. There should be a a vent pipe coupled to a pressure valve.

They 'blow off' at about 2 bar I thnk.


Christian.