If you felt like doing a bit of plumbing, you could buy a couple of new radiator valves tomorrow; turn off the boiler; drain down the system; remove the radiator, refit with the new valves, refill and you're away.
As a DIY man it would probably take you a good half day.
If you have to go to work instead you may have to pay someone else to do it.
However, if your TRV is fairly new and a current model, if you buy a new one you will almost certainly find it comes with a "decorator's cap" which is a plastic top that can be fitted in place of the thermostatic head and screws down to close the valve (the thermostatic head is removable) which would probably stop it letting water through.
Drain-down time is always a good time to do a chemical clean and refill with new inhibitor.
While it is drained down is a good time to fit any other new valves that might be needed; or thermostatic valves if you haven't already got them; or drain-offs if you haven't got enough.
As a DIY man it would probably take you a good half day.
If you have to go to work instead you may have to pay someone else to do it.
However, if your TRV is fairly new and a current model, if you buy a new one you will almost certainly find it comes with a "decorator's cap" which is a plastic top that can be fitted in place of the thermostatic head and screws down to close the valve (the thermostatic head is removable) which would probably stop it letting water through.
Drain-down time is always a good time to do a chemical clean and refill with new inhibitor.
While it is drained down is a good time to fit any other new valves that might be needed; or thermostatic valves if you haven't already got them; or drain-offs if you haven't got enough.