my only concern is that the wire from fcu to wireless unit is running across the gas pipe .
does the regs permit this or should gas / electric be certain difference from each other.
There's meant to be separation of at least 25mm to cables etc, and 150mm? (i think) to switchgear,meters and the like.
However - its not an uncommon situation, most boilers end up with random wires having to cross over the pipes below the boiler.