The Leopard at the Bottom of our Garden

Rebecca wasn't very happy when i found four of these lurking under an old sink we have in the back garden. "Slugs!", she said. "Get rid of them. They eat my plants!" However, I left them where they were, as Leopards are more attractive than your common-or-garden slug and they only eat other slugs and rotting vegitation.

Fingers crossed I've identified them correctly, or else Rebecca will have my guts for garters!