Instructions:Enter code at checkout. I've had this emailed to me as an existing customer - I've just used on some sale items and has worked fine. I did try at additions first (cheaper prices but have to pay delivery) however didn't work.
Full details from email:
20% discount offer: The promotional code may only be used once before 14/06/2011 and is subject to account status. Returned goods, financial services products and delivery charges will not count towards the value of the order. This offer cannot be used in conjunction with any other discount or promotional offer. Promotional codes are codes that enable customers to obtain benefits such as discounts, free delivery and free gifts. These codes are non-transferable so may only be used by the person to whom they are issued and must only be used in accordance with their terms and conditions of use. If you use a promotional code to claim a promotional benefit, you must first check that it was issued to you and that you are eligible to use it. By using it to claim a promotional benefit you will be confirming that: (i) you are entitled to use the code; (ii) you meet all the conditions that apply to its use; (iii) you agree to the terms set out below. If, before accepting your order, we find that you are not entitled to use the code or do not meet all the terms and conditions of its use, we may reject your order or alternatively process it without the promotional benefit being applied. If, after accepting your order, we find that you were not entitled to use the code or did not meet all the terms and conditions of its use, we may reverse the benefit that you obtained. If you transacted on a cash basis e.g. by debit or credit card, we may take a further payment, equivalent to the value of the benefit obtained, from the card used. If you transacted on a credit basis, the value of the benefit obtained may be charged to your credit account. We reserve the right to withdraw this promotion at any time.