[Arran]

Acetone will melt most old glues off, or old fashioned methylene chloride paint and varnish remover. The only issue is what sort of plastic they sued to make that socket? If it's some sort of phenolic plastic it won't be a problem, but if it's polystyrene then you will have to try the mechanical method of removal. Straight two part epoxy works well on phenolic plastics, I would use the 24 hour type as it's a stronger bond, don't use JB weld for obvious reasons, the 18 kv will cause problems with that.
Regards
Arran