[Arran]

 Perhaps the cabinet could be fumigated, like inside a tent, this is how they kill termites. But I think that baking it in the oven would probably work, at not too high of a temperature of course. I would not try making a device using bits from old microwave ovens, those are tuned to boil water and have whatever you are heating rotate in front of them, using a magnetron on a stationary wood cabinet may leave you with a burn mark in one side.
Regards
Arran

P.S I didn't realize that woodworm was actually a form of beetle, maybe those a relative of a powder post beetle? Mind you powder post beetles eat wood in adult form. In any event they are not that common over here, the only set I had that anything like that in the cabinet was a Rogers that was improperly stored in a shed or something since the veneer laminations are lifting in places. Nothing was alive in it when I got it, and after I cleaned the cabinet I sprayed it with pesticide, and have not noted any new activity since.