Hi Africa
The first one is a
Lehmannia sp, there are currently three in Britain. The Greenhouse Slug (
Lehmannia valentiana), the Tree Slug (
Lehmannia marginata) and
L. nyctelia.
L. marginata won't have the centre band on the mantle seen in your photo.
L.valentiana and
L. nyctelia really need to be dissected to be sure. Your photo is probably
L. valentiana as
L. nyctelia is mostly restricted to heated greenhouses...though it has recently been found naturalised in a garden in Devon.
Have you got a photo looking down onto the second slug, not quite sure what it could be...i'm thinking
Arion flagellus?
Regards Chris...