[Scribbler]

The only reason I left them in the greenhouse (growing in a cat litter tray) was to keep them pest free!!

Now greenfly seem to have got in. What can I do? Soapy water? Put them outside (for the slugs to eat)?

[sunshineband]

I would try wiping them off with soapy fingers, or spraying hard with water... don't let them climb back up though.

If you put them out then birds might help you out -- blue tits love greenfly  Some people use slug pellets but I rely on torch light scrutiny and beer traps  Each to their own on this one 

[strangerachael]

Go on a ladybird hunt. Every time I find a ladybird at the allotment I carry it over to the broad beans where hopefully they will be ready and waiting for when the blackfly arrive.
Ladybirds eat lots of aphids and their babies eat even more.