The charge for each Advertisement or for Artwork (or the total charge for a number of Advertisements and Artwork) shall be that set out on the respective Advertisement Order or that which may be calculated from the Rate Card applicable to the Advertisements or Artwork concerned. If a reduction is shown in respect of a promotional offer and you continue to meet all the terms of eligibility relating to that promotional offer then the charge shall be reduced by the amount shown but not otherwise. Terms of eligibility for promotional offers will be made available by us on request. Unless otherwise agreed in writing, payment in full shall become due and payable from you on demand. If payment is to be made in installments and if you fail to pay any instalment on its due date then we shall be entitled to demand payment of the unpaid balance including all arrears. We shall be entitled to charge you interest on overdue payments at the rate of 4% per annum above the then current base lending rate of HSBC Bank Plc. Interest shall accrue on a daily basis from the date the payment became due until you make payment of the overdue amount.