Please do not use slug pellets in your garden. Supposedly many modern pellets are not going to cause harm. However, in my view the risk of liberally spreading slug pellets around is too great. I have plenty of “tame” birds I do not want to be harmed, and the occasional hedgehog snuffling about. There is nothing worse than having precious seedlings destroyed overnight, or the continual munching of plants in pots to weaken ones resolve. There are more effective (and cheaper if you are not too squeamish) ways of dealing with them.
Biological slug control has been around for quite some time now. Parasitic nematodes (microscopic eelworms) attack slugs and infect them with bacteria. You already have these in your soil as a background predator. To make slug control more effective you only need to increase their numbers.
There are several suppliers of these nematodes such as www.defenders.co.uk, who for a tenner will send you some in a packet. Mix this into eight litres of water, and then pour one litre of that into and eight litre watering can and start watering. That is it. The effects take a few weeks to kick in, and then there is a noticeable absence of the blighters. Repeat the following year, and thereafter when you see slug damage. Its odd when you see a slug and do not recognise what it is.
If you are not too squeamish you can do a DIY version. Collect plenty of slugs into a jam jar or other container with airholes. Ensure they have a supply of food. When you have say 20 or so put them in a bucket or similar with an inch or so of water. Have the slugs on a floating island of vegetation. Make sure the container is covered. Let it brew and stir occasionally. If a slug is infected already it will spread to the others and then into the water where the nematodes thrive. After say a fortnight strain the liquid into a watering can, dilute and spray. Gather more slugs and repeat. Eventually you will be unable to find any slugs.