What a care sheet can't do, and was never meant to do, is replace a vet. Husbandry guidance covers what a healthy animal needs day to day: the right temperature gradient, appropriate substrate, correct lighting, a sensible feeding schedule. It doesn't, and shouldn't, attempt to cover what to do if an animal stops eating, shows changes in behaviour, or displays anything that looks like illness or injury.
That distinction matters because the two things get blurred fairly often, especially by keepers newer to the hobby who search online for symptoms and end up adjusting husbandry based on guesswork rather than getting the animal seen. Reptiles are also good at masking illness until a condition is fairly advanced, which is exactly why waiting to see if something resolves on its own is rarely the safer option.
Anyone new to reptile keeping quickly notices that the words vivarium, terrarium and enclosure all seem to describe more or less the same thing, and get used almost interchangeably across the UK pet trade. That overlap isn't a mistake exactly, but it does confuse more new keepers than it probably should, so it's worth untangling.
A quiet room, away from heavy foot traffic, loud noise or other pets, helps the settling-in process considerably. Some reduced appetite or reduced activity in the first day or two is common and not automatically a concern, since travel and a new environment are stressful events for any animal.
Enclosure space is the second consideration, and it's one that catches a lot of new keepers out. Many species sold small as juveniles need considerably more room as adults, and an enclosure that felt generous at first can become cramped within a year or two. Researching the adult size of a species, and the enclosure dimensions that go with it, before bringing the animal home avoids the costly cycle of upgrading tanks every few months.
Care sheets are one of the most useful tools available to a Reptile Centre care sheet library keeper, setting out the basics of temperature, humidity, diet and enclosure size for a given species in one place. Northampton Reptile Centre publishes care sheets covering species including the Hermann's tortoise, leopard gecko, corn snake and White's tree frog, and they're a sensible starting point for anyone researching a species or double-checking their current setup.