Have recently had a problem with snails entering house from garden. They are grey in colour .Wondered if anyone could identify and suggest what might kill them or deter them from coming in. Any help would be appreciated.
Close the door? The only way to get rid of snails and stuff is to hand pick them and dispose of them. You could also try putting a line of salt on the ground around doors etc however this will wash away when it rains. Stop cooking those cabbage dinners.
Not really enough to identify them by that description! You could try http://www.biodiversityireland.ie/ and see if they can help.
In terms of deterring snails, aside from picking them up and removing them, they don't like to cross copper, so a strip of that would deter them, they don't like to cross egg-shells or anything similarly spiky so a barrier of that is also a possibility. Also there are certain herbal plants that they don't like (not sure but I think lavender is one of them) so planting those near an entrance should discourage them.
Are you feeding the cat or dog in the porch? Check that there aren't any food scraps attracting them - they love cat food.
I have a salty spray bottle (old cleaning fluid bottle) inside the hall door and every now and then spray the porch. Problem solved.