I believe the snails to be:
Cepaea Hortensis - Yellow - Many Bands,
Cepaea Hortensis - Yellow - No Bands,
Cepaea Nemoralis - Yellow - No Bands.
No interactions present.
I'd recommend this site for help with identifying Cepaea: http://www.conchsoc.org/aids_to_id/sneqnou2.php
... and of course the advice of the snail experts on iSpot who really know their stuff!
Also take a look at the Evolution MegaLab which will tell you all about Cepaea: www.evolutionmegalab.org
University of Edinburgh and Biodiversity Observatory (OU)
Yes to them being Cepaea snails, and the first photo does look good for C. hortensis, but I'm not so sure about the others - they look quite old and bleached, and I don't know how persistent the banding is. It's safest to identify live snails if you can find them, or if they are empty shells then look for fresh ones.
Entomologist and biological recorder
wow, thanks for all the replies! I'd almost forgotten all about putting my observations on this site..
As it happens I undertook the study of the Cepaea for the evolution megastudy. In the end I just went through all of the other Cepaea observations on this and other websites to help identify the snails I'd found. However, I ended up discarding some of my finds because, as Martin said, they were just too faded.
Lat/Lng: 50.90736, -0.13037
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