You need to go out at night with a torch (preferably on a drizzly night!) before you can say there are no snails. They often ignore pellets - Busy Lizzies are so much tastier. I still back slugs & snails as the culprit.

I squashed a slug (with orange fringes) that was 9inches long the other night. I admit it was stretching from one petunia to the next but it was an inch longer than my hand span.

Good night! The Olympic Peninsula Banana Slug has reached Great Britain!

That made me look it up Tugbrethil. Your suggested slug is spotty & mine are plain creamy yellow or light brown. I think I had a large Arion ater (Black slug, but a paler variant) or Arion vulgaris (Spanish slug). I see that the Olympic Peninsula Banana Slug is a descendent of European Black Slugs. We had them first! :-)

I didn't know that, Beattie! The Banana Slugs are pretty variable: some are nearly black, while others are a light yellow. They don't hang around here (thank heavens!) but I have occasionally seen them on a shipment of plants from Oregon.

They are in Slug Heaven here Tugbregthil. It's relatively cool & damp in the summer & we don't get a lot of very cold weather. The odd frosty night in winter, so they breed like rabbits - of which we have a lot as well. And there's no shortage of snails either - we have crunchy garden snails - Helix aspersa and banded snails like Cepaea hortensis. Pass the torch! :-)

We have the decollate snails, which are sold for the control of garden snails, but if they don't have garden snails to eat, they eat plants. Also a little gray slug that I can't remember the name of, now. Usually only a pest in overwatered areas...and veggie gardens!

We have bucketloads of the little grey wet ones, I think they're called field slugs.
All of Cornwall normally counts as "overwatered" it's remarkably rainy for a holiday area!