Our house smells of oil.

[SmileItsSunny]

We recently had our oil boiler serviced, and since then can smell oil in the house, most noticeably in the corner behind the boiler. The engineer has been out and says he can find no sign of a leak.

Also, the electric thermostat gadget doesn't work. Once the system is on, it is ON and you can't persuade it otherwise. Also, we can't have heating and hot water on at the same time .

Who should I call? Plumber? Electrician? Oil boiler service technician?

You need a better oil boiler engineer.
Ask friends and neighbours for a recommendation.

I think you have a leak, it might be in a hot place that dries quickly.

The thermostat and valve should be straightforward.

Hmmm, thanks Piglet John. Nothing has improved, we used the neighbour's technician this time! Will have to ask different neighbours :-)