On 30 Jun, 22:03, " wrote:
Tiredness and smell of gas.

It *could* be unburnt gas from the boiler, along with carbon monoxide.

If you haven't done it already, get that boiler checked very soon.

Is there a brick flue adjacent to the areas where you get the
occasional smell? One (remote) possibility is that there has been some
deterioration of the flue structure allowing flue products to
percolate through the plaster and into the living space. Many terrace
houses have a staircase which backs onto "next door". A possible
problem might occur from next doors flue and the possibility exists
that there was no leakage while Transco were present.
I have in the past been witness to a case involving poor building
practice allowing leakage into a bedroom from a coke boiler exhausting
into a brickwork flue with gaps in the mortar and spacing, but
concealed by plaster. Rare but it led to long term health
deterioration until it was traced and rectified