Turned out this was fortunate as I noticed a small spiky ball on the edge of the stone I turned to pick some specimens from. A quick handlens examination came up trumps with a Spiny Snail (Acanthinula aculeata) and alongside it another small snail. Double the size of the first but still pretty tiny - Lauria cylindracea. Still on the same small stone the size wars continued as there was also Punctum pygmaeum. A lovely trio of tiny snails, like some kind of Mollusc nouvelle cuisine. All went into the smallest pot with oodles of space to spare.
And the numbers bit: