You can try the age old remedies of using the remains of your halved grapefruit, placed face down on the soil, leave for a while and then up-turn at night. You'll find it full of our dear slimy friends. Better still, three quarters fill a jamjar with cheap beer, sink into the garden so the rim is level with the ground. The slugs drop by (literally) for a drink and drown/die happy. My favourite? Wait until the small hours and arm yourself with strong torch, a bucket and trowel and go hunting! I've caught over 60 in one night and it gets quite addictive!