Curing a seeping Sunvic Thermostatic Radiator Valve?

I have recently discovered that one of my TRV's appears to be seeping from the centre spindle when the central heating system cools down e.g. overnight when there is no heating on. I have shown three photos showing the TRV in-situ (two without the top cover) at http://www.roadster.myzen.co.uk/sunvic.htm

Point A indicates the area which the water appears to be seeping from.

Point B shows the base of the TRV. Is it possible to remove this or any other part of the valve without draining the system? I had thought about winding some PTFE tape around the thread (if it's possible to remove it without draining down).

I have only recently drained down the entire central heating system covering three floors because I needed to replace a radiator which had developed a leak along the bottom seam. After replacing the radiator and whilst re-filling the system I added corrosion inhibitor. If I have to drain the system again, the adding of the inhibitor would have been a pointless excercise.

Thanks in advance for your assistance/advice.