There are millions of winkles about, but not quite as many millions as I had first thought: Lots of them are in fact dog whelks, which taste shit.
It didn't take long for Leo and I to gather a couple of handfuls of the critters, despite the fact that Leo didn't help at all. He did, however, pluck one winkle off a rock, hold it up to his face and say "are you ok?" before quickly launching it as far as physically possible. Didn't even give it a chance to answer - guess we'll never know.
After letting the crustaceans purify themselves in salted water for a few hours...I cooked them to death: Fried some onion, carrot, garlic, and then added a handful of bladderwrack (because it was growing where the winkles came from) and a bit of water. I added the winkles to the pot, put the lid on, and steamed them for five minutes.
Then I ate them, which is very satisfying (if you haven't done it before): You stick a pin or a cocktail stick into the opening and pull out the good stuff; a wierd slimy grey curly thing. It's a bit off putting at first, but when you stop and think what a mussel looks like...Anyway, I will definitely eat them again, but give dog whelks a miss (maybe they taste bad because they are carnivores). My winkles were nice, though - not at all tough, like you would expect.
Winkles and Dog Whelks are fortunately quite easy to tell apart: Dog whelks have a white/ grey shell, with a distinct groove on the rim of the opening, which is where they shoot out their evil sucker thing. Winkles are more greenish/ dark grey, and usually squirt a bit of water at you when you pull them off a rock. Which is fair enough, really.
ps The above is also another way not to eat bladderwrack. There must be a way...