Rusty Hinge 2 writes
The message
from "Mary Fisher" contains these words:

I've picked slugs (only large ones) from the roof of the greenhouse, seen
them at the top of the garage wall and on the outside of the bathroom
window
pane. The bathroom is on the first floor of an inter-war house, i.e. it's
not a modern, low ceiling'd building.

I'm told that the big (BIG) slugs only eat rotting stuff and algae, so
if you have any pleurococcus (or similar) on your greenhouse, they might
do you a favour.

New Scientist had an article a year or two back about using slugs to
control bathroom algae. The best were the pretty yellow and grey ones.
--
Kay