Tim+ wrote:
Hardly beyond the wit of man to design a lightweight well ventilated
weather-proof enclosure that would avoid the build up of any gas if
required.

Of course. But you're trying to do this without building control. The
point being that you can do whatever you like, but it's up to you to show
BCO that it's suitable. Anything that's 'special' is likely to require the
sort of one-off scrutiny you're trying to avoid.

A bit like how you /can/ install your own consumer unit, but you need to get
that signed off by the BCO to confirm it's up to scratch. Alternatively
there exists a competent persons scheme of people who do it day-in day-out
and can sign off their own work - this is often cheaper than BCO signoff and
is designed to handle the large volume of run-of-the-mill installs more
efficiently than getting a BCO out each time.

Theo