I think I have just about given up on the slugs - they seem to eat EVERYTHING - not just hostas, but any little plant. My new theory is to concentrate on the things that they will avoid. So far they have left my geraniums alone (things that continental people put in pots - pelargonums?, not traditional English bedding). Can anybody think of any other plants that they will avoid.
Meanwhile, my neighbour claims that he has no slugs. Didn't go into detail, but I suspect he is nuking them and they are setting up little refugee camps in my garden