Theirs tons of animals we'd happily keep in UK waters. I've seen lots around Scotland but I think I've seen some of the best ones around the south of Ireland and west of England/Wales areas. Theirs anemones, different fancy stars, hermits, feather dusters, corals, the list goes on and theirs plenty of nice looking colourful ones too. It surprises me that they're not collected a lot but theirs also problems in the waters with so many boats travelling through them and trawlers are destroying them every day, it's only quite recently that it's all been noticed and the effects have been noticed, I think a lot of places are trying to get stricter laws to save them but I doubt they're going to get very far, the boating/fishing community are going to be much bigger than the people studying these animals and by the time they have solid proof and then work at creating laws to protect them I expect the damage will be done and that's even if they're capable of doing anything.
If I remember right the best place is south of Ireland where theirs a few little islands, one of which has the worlds population of a certain bird which uses only that island. It's full of steep cliffs and unexplorable by foot but all the bird poo covering the cliffs washes down into the sea filling the waters around it with tons of nutrients giving life to a massive amount of sea creatures.