right, now you're up to speed :-) can you see any problems with the cable
run
following the gas pipe in the diagram depicted in my original post, in
relation
to the various regulations ?

Well a quick look shows that it is non-viable, as you may not conceal wiring
behind the skirting board unless mechanically protected or bury it more than
50mm deep.

You might get away with it ELV (although I'm not entirely sure on this), but
this will require a relay at the boiler if the boiler isn't already ELV on
its thermostat connection.

Christian.