Radiators not working consistently

[TheXxed]

My radiators will not switch on and then miraculously switch on by themselves. I called out a plumber when they wouldn't switch on and he said it was the electrics, I had a phone conversation with an electrician who said he it was most likely a pressure issue and be didn't want to take my money for a job he can't fix.

I am at loss and very chilly.

[PigletJohn]

you have a gas boiler, right?

And a timer or programmer for the boiler, and a room stat on the wall?

And do your radiators have thermostatic valves as well?

What are the settings on all these controls?

Photographs might help.

Have you got a hot-water cylinder?

Does the boiler have a pressure gauge? What does the gauge read (a) hot (b) cold?