Where to find nail polish?

In the UK we have lots of different nail polishes such as Revlon, Rimmel, Natural Collection, Maybelline, N07 etc. I buy the ones from Natural Collection and they are �1.79 I think which is $2.586. The more expensive brands such as Revlon and Rimmel are around �5-6 each which is around $7. These brands can be found in Boots the chemist and some supermarkets such as Morrisons or Sainsburys.