We're really sorry to hear this! If you paid by PayPal, please use the Contact Us form and send us both transaction IDs so we are able to look into this and refund the relevant transaction.
If you paid with Sage Pay you will have two transactions and more than likely one of the payments will have failed and one will have processed normally. With the failed payment transaction the money will have likely been taken out of your account or is being held by your bank. This payment should return to you within a couple of days but if it doesn't, get in contact with us and we will look into it further for you.