While pulling up some gone-far-too-rampant shrubs from one of the borders last weekend I found lots of snails, including this shell from a Roman or Burgundy Snail (Helix pomatia). This is an edible snail brought to UK by the Romans and still to be found some places in the Cotswold. In the absence of a living specimen I think the shell is probably a souvenir from a trip to the National Trust’s Chedworth Roman Villa, as while they might have been living in UK for hundreds of years, so far this lazy snail didn’t manage to spread very far - unlike many of its mollusc relatives. Too bad! Chedworth by the way is a really nice place to visit for both archaeology and nature, more info here: https://www.nationaltrust.org.uk/chedworth-roman-villa/features/wildlife-among-the-archaeology
Yanking out overgrown plants, I also found a nice selection of Brown-lipped or Grove Snails (Cepaea nemoralis). These are pretty snails, varying in their colour quite a lot. Apparently they are also edible, but you would need a lot more of them than of their Roman relatives to make a meal.