I've always assumed these little blue butterflies in my garden in Paignton are Small Blues but, having just googled them, I'm now not so sure. It's on a hardy geranium flower. I didn't manage to snap it with its wings open.
@Gigit Usually the only 'blue' butterfly that comes into gardens is the Holly Blue- and they seem abundant this year too. But this isn't one- the markings on the closed wings are quite different- probably a male Common Blue by the look of it.