Here's a quick look at Butter London'sHen Party, which I find works best as a layering polish. I already had Dosh (drab apple green shimmer) on, so I applied a coat of Hen Party over it. The blue iridescent shimmer in Hen Party is really quite beautiful when the light hits it, and the sheer milky base tones down Dosh down a notch or two.
The more I use Butter London polishes, the more I love them! And to think I never even had any until this year. I just wish they'd have some good codes or sales to bring the price down a little, but I do enjoy their formula and shades.