It's not so much the rates that change every year (although they have this coming year in a rare simplification measure by Gordon) - it is usually that the rate subject to tax rises each year so as to counter the effect of inflation (or less than the effect if the government has a funding shortfall!)
Everything in the UK is conventionally quoted pre-tax.
A tax accountant (I am not tax) told me over a drink that the UK is actually quite lax in the tax rates - though shocked for a short while, my colleagues seconded the New York have discovered that although federal taxes are OK, state taxes on top of those can make overall tax shockingly high...!