What are they doing? I've not noticed snails partially exposed for long periods before!!
Is it sex? Are the blue bits on 2012090106 eggs?
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You have at least two species in the photo; the smaller with 5 dark spiral bands and brown lip is Brown-lipped Banded snail, Cepaea nemoralis; the larger with the mottled brown shell is probably a Garden Snail, Helix aspersa. Kind regards
Lat/Lng: 53.599916, -2.259398
OS grid ref: SD829115
My back garden