My wife has raised a number of local snails, Oregon Forest snails mostly, in some of the 10 gallon tanks I have kicking around. They do exceptionally well inside, we had ours in the kitchen.
Starting from the bottom of the tanks I put a layer of sand, garden soil, then leaf mulch. Then some rocks, sticks, leaves etc. Typically, we do not put a water dish in but if you were to go away for a while I would. Moisture comes from misting, and like some reptiles it is best to mist the sides of the aquarium too. I used aged water for the misting, but I would have to say I haven't noticed that city water has that much of an affect. Feeding is normally lettuce, not the iceberg kind, zucchini, other kitchen waste. We feed daily and all the snails in a 10 gallon aquarium would eat about 4 1/4" slices of zucchini per day. You have to totally clean out the tank from time to time and remove any food before it starts to decompose.
The snails had multiple generations over the winters and did not seem to have a need for a hibernation or an estivation time period.
My wife was a teacher and we used our snails to breed classroom sets of snails for the students to raise and study. During her mollusk unit each student was given a snail and a snail home to raise their snail.
https://en.wikipedia.org/wiki/Grove_snail - introduced to NA so if you catch do not release... Easy to raise, we found ours in our garden
https://arocha.ca/portfolio-items/oregon-forestsnail/ - Easy to raise not as easy to find
https://en.wikipedia.org/wiki/Monadenia_fidelis - not easy to find compared to above, not as easy to feed, like more lichen and fungi.
The
Haplotrema genius is pretty common in our area, you cannot put these in with your other snails because they are carnivores. We have kept these as well but they are real hard to feed, we feed ours raw chicken but I wouldn't say they thrived.
https://linnet.geog.ubc.ca/efauna/Atlas/Atlas.aspx?sciname=Haplotrema vancouverense (further checking suggest this genus is not found outside North America, just noticed you are writing from the UK)
The grove snail for the UK would be my choice, they have a number of possible colors and patterns and easy to raise.