For hostas in pots, try spraying around the base with WD40 (top tip from a hosta grower) it does work, but obviously can't do that with hostas in the border! Just make sure leaves aren't touching shed or another plant that the slug can airlift in by!!!!
Also we have heavy clay, it's actually yellow when you get down a bit. Mulch for England. Dig well rotted compost in where poss and then mulch. I tend to use peatfree organic, some are really reasonably priced - Vitalearth 4 bags for £10 currently. On the plus side of clay - roses love it!
All the best