Hi My solution is very simple and has proved to be effective. At between 2300 - 2330 every evening (especially if it has been a warm/wet day and the tempreature stays warm) I go out into the garden with a torch. The more powerful the better.
You will see slugs and slug trails which will enevitably lead you to the offender/s. Pick them up and and pop them into a container filled with heavily salted water. This will kill the slugs. Snails on the other hand need to be crushed. Don't know why but they seem to be able to survive for over two hours in salt water and in that time the slime their way up the side of the container and escape.
The following morning tip away the salt water and if you put the slugs in an area accessible then sometimes the birds/hedghogs will eat them. Good luck and good hunting.