Manc guy, for your own and family's safety, go down the local hardware store (or the uk equiv. of 'home depot') and buy yourself a couple of plug-in CO detectors (carbon monoxide). They cost no more than $25 (10 quid?).
Plug one of them near the boiler, and the other close to your family's sleeping area.
Then strongly insist on an inspection/certification.
Plug one of them near the boiler, and the other close to your family's sleeping area.
Then strongly insist on an inspection/certification.
