As seen during our appearance on BBC Gardeners World we use garlic wash as a slug deterrent on the nursery. Please find below the recipe that we use and find very effective. The quantities aren't exact and you can always alter them as you wish.

Store outside in a cool dry place or in the fridge. Can be used throughout the season, make a fresh batch every year.
Open a window because it's going to get garlicky!
Attention Customer
Due to the extreme heat this week, all orders will be dispatched W/C 29th of June.
Apologies for any inconvenience caused.
Thank you in advance for your understanding.
Sienna Hosta Team