Hoping someone can help answer this question, I’ve googled it but doesn’t address my situation. Radiators only working intermittently.

I moved into a flat recently - UK and have found that my radiators only work sometimes.

I have the heating turned on all the time on the control panel and then just use the thermostat to actually turn it on / off by adjusting the temp up or down.

50% of the time I turn the thermostat on and they heat up nicely, the other 50% they remain ice cold. Not partially warm, or warm at the top/bottom but totally cold. Also I did bleed them all recently.

Any ideas what would cause this given it is set to on all day and I just use the thermostat to control it? As I say it’s 50/50 whether they will come on.

Thanks