You have several choices, slug pellets, surround young plants with coffee grounds, crushed eggshells, gravel. citrus fruit skins are another deterrent.

or pop outside in the evening with a torch and catch the little blighters.you may look a bit mad but you would be amazed how many you can get.happy hunting.

tanx 8)

if not a little dish with a drop of beer , i know its a waste of booze, buts its that or what amblealice and plantmaiden has put .But there are special slug catchers you can buy , you sink it into the ground and the slugs fall in.
A garden centre or b and q should sell them