I've just got my 'Green Gardener' catalogue through the post this morning, and it has lots of anti-slug things in it, including nemaslug, they have one-off treatments, and treatment programmes, meaning you get one pack every six weeks, so it kind of reminds you you need to re-apply it. The standard pack (3 packs, so 18 weeks' worth) costs 32.50, and treats 40sq m (50sq yds). They've got other stuff in there too, including slug tape (does work, I've tried it from ebay), shocka rolls & mats (thinking of getting some of the mats for my strawberry planters), slug gone, copper bands, hosta halos and a range of slug traps.
I'm not connected with the company in any way, but as I have lots of birds and a couple of frogs in my garden, try to garden in a way which won't harm them, as they are a joy to see in the mornings, I'd hate to harm them in any way by using slug pellets. I'm also going to try growning caulis, sprouts and broccolli this year, and I've heard that the slug gone is very useful to use as a mulch around them.
They also have other stuff in there, including ladybird larvae, glue bands, sulphur rose (for treating blackspot), you name it, they have a biological or eco-friendly way to control the problem. I could spend a fortune there!