One radiator always on, boiler and boiler room always warm!

[OilBoilerNoob]

My apologies as this question has probably been asked loads of times.

We moved into a new house in Jan which has an oil boiler, the room that houses the boiler is always warm, sometimes like an oven.
The radiator that's directly above where the boiler is is always on, mainly warm but sometimes really hot.

As I'm new to oil boilers and with the room that has the 'always on' rad being my daughters room I had an engineer out to look at it.

After his fist visit the boiler would no longer fire up when the hot water was turned on, maybe his fault, maybe coincidence, i wont get into that now.
So he ended up replacing...
The circuit board, thermostat?, return valve I think and the sensor that fires the boiler when the hot water is turned on.

After all that the radiator in my kids room is still warm, it hasn't got as hot as it did before but still on never the less.
The boiler/boiler room is still warm, again it's not getting as hot as it did (so far)

I know that oil boilers have to keep a certain amount of water hot for an instant run off, so I'm guessing now he's replaced the thermostat it will stop it from over heating the 'instant' hot water which is why the room and rad are only warm now and not boiling.
But is it...
Normal for the boiler/boiler room to be noticeably warm?
And is it normal for a rad to be always on?

Boiler is a,
Firebird Enviromax Combi
C26 Slimeline
Fitted 2014

 

[SimonG]

So it will be a twin pump model. Sticking non return valve.
If you had no hot water after the visit it could have been a thermistor issue.

 

[OilBoilerNoob]

So it will be a twin pump model. Sticking non return valve.
If you had no hot water after the visit it could have been a thermistor issue.

Thermistor! That's what he replaced not thermostat.
He apparently replaced the return valve.

So is the heat from the boiler normal?
And am I correct in saying that there's still a return valve issue if the rad is still getting warm?

 

[exedon2]

Its a heat store combi so as long as its switched on it will be hot.
As Simon says sticking non return valve on heating pump cause of rad getting warm.