tonyjeffs wrote:
Thinking some more about the legal aspect, the legality itself is not
an issue.
The real problems are
1) Buildings Insurance (If a claim was disputed , how do you prove
'competence' in a civil court?),

Well my buildings insurance excludes "systems... which have not been
installed or fitted by a suitably-qualified workman" so according to
that, the "competency" issue is not relevant to the claim. I imagine
the fire brigade and/or insurance loss-adjusters would usually be able
to determine the cause of a gas or boiler-related fire, and if it proved
that poor installation was the cause, the insured may have problems if
they can't say which installer was responsible (or demonstrate that any
such predates the insured's ownership of the building.

and
2) Selling your Home (Do you have the correct paperwork to satisfy the
buyer's solicitors?)

Done to death in this ng many times!

David