You will not pay any stamp duty on any property priced at £125,000 or less. Over this value, you will pay Stamp Duty Land Tax at 2%, and then in rising increments until 12% on properties over £1.5 million. However, if you are a First Time Buyer then the rules are different and you will not pay any stamp duty on any property priced at £300,000 or less. The tax you pay will begin at 5% between £300,001 and £500,000, and thereafter rise steadily to 12% on properties over £1.5M in line with normal Stamp Duty rates.
If you are purchasing a property as a second home, or with a buy to let mortgage, your stamp duty rates will be higher.