Posted: 17/10/2012 at 17:57
You really do need to go out at night with a torch and have a look, you'll be staggered by the number of them around especially during warm wet periods. I tend to deal with them by using something sharp and planting a patch of some cheap plants, that I know they like, to tempt them to a certain area (50p trays of unloved Marigolds from B&Q were this years choice). Snails get a slightly more under foot treatment.
You can also use beer traps and there's a thread on here about a flour trap somewhere. All the methods mentioned work, you just need to pick one and stick with it when there are plenty of them about.