OPTIMA 1001 BOILER - HW WORKING BUT CH HAS MIND OF ITS OWN!

[cockers]

I have an Optima 1001 Boiler which is about 8-9 years old, when I moved in 3 years ago I have always put the heating on whenever I need it on and I would do this by turning button to continuous heating and turning off when finished.

The problem is all of a sudden the continuous heating won't come on at all as the pilot doesn't fire up. The pilot does fire up for the hot water though, and the other strange thing is that the heating does come on for half an hour at a time randomnly. My housemate swears he hasn't touched the timer/settings, so I have no idea! My problem is I haven't got a manual for the boiler!!

Can anybody help?

 

[twgas]

does the pressure gauge read 1 - 1.5 bar

 

[cockers]

Yes between 1 and 1.5

 

[twgas]

do pump and/or fan run when you turn on CH

 

[cockers]

A noise happens like its about to start but it just stays like this without the pilot light coming on. I'm presuming this will be the fan and not the pump.
Like I say the weird thing is that over last 7 days the heating will come on but not for very long, I was hoping that maybe the settings were tampered with and maybe it is coming on by a timer but I have played about with it and no matter what setting I put it on Continuous Heating just doesn't come on.