It's not too hard to go ahead and cook the oyster, at which point I typically find them okay, though I generally prefer them to be included in some larger dish as opposed to on their own.
I'm not familiar with ormers. What are they?
I did not know what an ormer is, either. Apparently it is a sea-snail in the genus Haliotis, which includes abalone? They sound like something I'd very much enjoy eating...cooked.