I love Models Own nail polish as they have great coverage and are very reasonably priced. There are usually offers at both their site and in-store at Boots too. They currently have a free nail art kit if you spend £25 or more on the Models Own site if you use the Promo Code NAILARTKIT.
I have used Purple Ash as a base. I needed 2 coats for this. I then used Jack Frost from last year's Wonderland collection to create a glitter fade. A very simple but eye-catching design.