After much annoyance with slugs destroying favourite plants in my garden (and I had tried slug pellets though I didn't know they were so harmful to birds etc., also sand and the like), I was told to try putting down porridge oats.
I placed the porridge oats on the border in a erm.. border line form and found these 'pellets' saw off the slugs no problem.
How it works, (do not eat your dinner whilst reading this!) the slug eats the oat and it causes the slug's stomach to expand and burst. The bird/hedgehog/frog eats the slug and gets rid of it, and the wildlife itself is not harmed.