These animals are exotic pets so you won't find them in England. But you can buy them. They eat inverts but you you will have to do some research before buying one as they may need special care. Paddle-Tailed and Fire-Bellied newts can be kept together in a heated tank. Axolotls grow bigger and can be aggresive but can survive in a pond, however I'm not entirely sure if this is legal. You will need confirmation of that. I will post a picture of each creature. A good shop is Southern Reptiles (Cadnam), they stock all these species.
Hope this helps.
They are a lot more difficult to keep because they require livefood, heaters, UV bulbs, humidifyers, specialist equiptment and climbing apparatus. But... if you think you can handle that, they are very rewarding species and although harder to keep than newts or fish, they are some of the easiest species of exotic pet to keep. If you have friends who are reliable and don't mind newts or livefood, they can look after them. Also, reptile stores often do holiday keeping for a price...
Hope this helps