Well, I seem to be having some success. I have an electrically powered water pistol (originally bought as a squirrel deterrent) which, loaded with an ammonia solution, is remarkably effective although what the neighbours made of me lurking in front of the house at 11pm with a torch and handgun firing into the lawn I don't know.
And I bought some iron phosphate slug pellets and sprinkled them around. These little blue pills (not to be confused with other blue pills) are apparently irresistible to slugs which eat them, become sluggish and then slugger off to die. I put some on the patio last night and this morning found no blue pills but a lot of slug trails in circles but no slugs so it looks as if they work. Maybe they died happy...
Colin