It's complicated:
http://www.hmrc.gov.uk/rates/it.htm
Basically in the new tax year that's coming up soon, you get £5,225 (just short of $10,200) tax free and then there's a series of bands (10, 22 and 40%) depending on how far over the tax free allowance you go.
Also, I don't have any income to tax
Also also, UK income tax does not include compulsary national insurance payments which go towards your state pension.