Replacing radiator valve on a sealed combi central heating system

I've got a radiator with a broken thermostat valve jammed in the off position - hence the radiator has been off for months. I need to get it working before winter...
Is it possible on a sealed (Worcester 24i Combi-boiler) system to isolate the radiator so as to remove the faulty valve and put the new one on? Or does the whole system have to be drained?
There is another valve at the other end of the radiator. If I turn this off, and then remove the thermostat valve at the other end, will it just be the affected radiator that drains, or will there be a flood, or other problems?
Or what about freezer sprays for isolating pipes?
Or is it a job for a professional?
Thanks in advance - any tips or advice welcome!
William
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scrawled:

Hit it, gently. Sometimes the plunger doobrie behind the pin gets jammed.

Whole system needs draining, which isn't as bad as it sounds.

Nope, that won't make a bit of difference. If you were to just turn off that valve then when you removed the TRV the radiator would empty and also the rest of the system, all through the 2 holes where the TRV once was.

Never used it, I generally drain down to clear any crud out of the system anyway.

Your decision, might be safest?
--
Stuart @ SJW Electrical

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