I've often felt it is a great shame that we don't have populations of fire salamanders
in the UK. You only need to pop across the Channel to northern France and there they are. Although they range across Europe from Scandinavia to Morocco, their distribution is very patchy and represents remnant populations left behind after the last ice age, hence the reason why they do not occur naturally in the UK.
A friend of mine recently sent me this picture of an outdoor enclosure they've built for fire salamanders. If done right, outdoor enclosures work very well for this species. Unlike some species, e.g. smaller newts and highly agile frogs, they are less likely to escape by climbing out, and if they enclosure is well situated (not too much sun and some shelter), they are ideally suited to the British climate. This enclosure provides much more space than a plastic box and this species breeds well in this type of setup.
This enclosure is built from blockwork but I know of a very successful breeder in the south of England who used to keep Salamandra
in outdoor enclosures made from outdoor-grade plywood. Such enclosures need a layer of packed gravel for drainage and to prevent the animals digging out, then a substrate of soli, composted bark chips, leafmould, dead leaves etc. Rotting wood, stones and piles of bark provide shelters. There needs to be a water area, which for Salamandra
needs to be shallow and easy to climb out of to prevent drowning. Most important if the animals are to be left out all year is a frost-free hibernaculum ("hibernation" shelter) consisting of a deep sheltered area. Polystrene boxes sunk below ground levels or rockeries work well for this but must not be in danger of flooding. It can also be a good idea to add some protection such as bubblewrap or horticultural fleece across the top of the enclosure in very cold weather.
Once the enclosure has matured the animals will find some of their own food but will also need supplementary feeding with worms, slugs, woodlice, etc added to the enclosure. It's relatively easy to train Salamandra
by spraying the enclosure lightly at dusk or just after dark, a time when they are naturally active, and then adding food. They will soon figure this out and can then be observed without disturbing them, which overcomes one of the problems with outdoor enclosures, that it is more difficult to monitor the animals than in indoor setups.
The mesh across the top is not to prevent the animals escaping but to protect them from dangers such as rodents, dragonflies, birds (especially magpies) and cats. Sadly, it won't protect them from any two-legged vermin which might find their way into your garden, so an outdoor security light and a shotgun might also be necessary to ensure their safety.