no one so far has answered the question

I wonder if your damp bathroom,is the right place for your Orchids,young Alistair? The woodlice must be getting in from somewhere,as it's not usual to have them in the compost..I've never seen them in mine,even though I stand them outside sometimes,in summer,in the shade.
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I would be tempted to repot them all in some new specialist compost,having washed away all the old compost,checking thoroughly as you go..If you have
another window you could move them to..one with light,but not in full sun..and not near a radiator,..north facing,ideally,I'm sure they would be much better..Ok,a misting of the leaves and aerial roots occasionally is beneficial ,as is standing them on gravel in the bottom of their pots.but if it's permanently damp in their present position,I'm not sure if it's the right place..maybe check where and if,the Woodlice are able to get in ..the tiniest hole is enough..

I too wouldn't have thought that a damp bathroom was the right place for orchids. Ours sit on windowsills facing east(ish) and are perfectly happy.

Mine are in a room that has south and west facing windows but not direct sunshine

I've decided just to grow the small ones......more in the same space :0)

Just a point YoungA woodlice only eat rotting wood, and there shouldn't be any rotting wood in orchid compost.

A good point,Mg..I hadn't thought of that..