The3rd Earl Of Derby wrote:

Well they do come from outside thats a start.

The concrete floor area by the kitchen door in my house was where my
slugs where coming from.
On further inspection there was a flaw in the concrete which had
cracked and a small hole was revealed when I took of the skirting
board at the back of the door and the blighters where coming in
through the outside underneath the door sill.

Not saying this is where yours are coming from,but check your door
frame for rot around the bottom half? or possible they might be
getting in behind the sink area or through a air brick if you have
one? also check the perimeters of the brickwork/skirting/floor for
tell tale signs.

Damn forgot to add put salt down around the door area first for a couple of
nights and see if they still appear,if they do then you can eliminate the
door area as they wont dare cross the salt and then try another area some
where they are more frequently found.

--
Sir Benjamin Middlethwaite