I've finally found one that ticks all the boxes, it's vibrant, ever-so-slightly metallic, it has a hint of violet and the formula is great. It's Cosmic Blue from Avon's upcoming Nailwear Pro+ line.
It's good to go in two coats and dries really quickly. I've only had it on for two days but so far the wear seems pretty great too! They are meant to last up to 12 days... a pretty bold statement! I'll be interested to see if they live up to it.
They won't be available till the 10th May, but are quite a bargain at £6 each.