@jaker I think in your region the pipistrelles and myotis/vesper bats are most common? Both of those would love a multichambered bat house like this.
I think the biggest concern I would have for this design is how close the entrance is from the “ground” immediately below. Bats are quite vulnerable to nest predators like rats and cats if the entrance to their roost is within jumping distance. (At least you probably don’t have as many snakes to worry about as we do! 😅)
Basically the predators in the area quickly learn that they need only to wait below for the meal to present itself like clockwork.
The other aspect is that bat faeces/guano is a wonderful amendment to compost piles, but allowing it to fall directly on plants is a twofold concern. First it can burn more delicate plants, especially if you end up with significant accumulation if your bat house is very popular. The other possible concern is that without spending time in a hot compost pile, the microorganisms in the droppings could be a worrisome for your edible plants.
I have a few links to general bat house design considerations but since they’re southeastern US focused your bat orgs in Wales will absolutely have more tailored/specific recommendations.