I have been given by my mum a remedy for keeping slugs off my Hosta's so I will share with you all, this was tested last year and worked so give it a go.
2 Large garlic bulbs, crushed
2 pints of water
To Make: Boil together until garlic blanches, cool and strain then add water to make up 2 pints. Store in screw top container such as a jam jar. (remember to label - slugs only)
To use: Dilute 1 tbsp of mix to 1 gallon of water. Use a watering can with a rose to wash the leaves in late afternoon. Repeat every 14 days. (this only works once leaves are open so crushed stone/grit is good on the pot or covering the crown to stop slugs crawling over the new leaves)
Good Luck gardeners