Central heating issue

[raceboy]

Currently having an issue with a few radiators not getting hot, they have all been bled and there's not a drop of air in any of them, the valves would also imply the rads are 'on'.
Other radiators in the house are piping hot, it's just one in the en-suite, and two in the kitchen, one of those gets luke warm, the other stone cold all day every day.
My knowledge of these things starts and stops at bleeding them, so what do I try next before looking like an idiot to a plumber because it's something blindingly simple.

[raceboy]

The cold kitchen rad does have a decidedly dodgy looking TRV on it, just been reading something else that suggests tapping the central pin to see if it's stuck, that's going to be tonight's first job.

[raceboy]

Sheepshanks said:

If it's not that then it might be balancing - do they get hot if all the other rads are shut off?

No, tried that.

Sheepshanks said:

Is the system open-vented (with a small header tank in the loft) or sealed (with a pressure gauge somewhere?

Don’t think there’s anything in the loft, it’s a Combi boiler.

[raceboy]

Sheepshanks said:

Have the rads ever worked?

Not sure to be honest, I don’t think so.
Took the TRV off and the plunger could be pushed down, so don’t think it’s that, the pipe from wall to TRV is stone cold, I don’t think it’s plumbed in!