Hi db2admin,
Under the Sales of Goods Act you are obliged as the consumer to show a "proof of purchase".
Many consumers interpret this as being a receipt only but if you have used a Credit/Debit card to make the purchase then that will suffice. Just show the the line item on the statement.
Retailers are very much aware of their obligation to consumers under this act so spelling out the above should move them to action.
By the way, if they try to fob you off on dealing with a Distributor or Manufacturer for your compliant then also remind them that as you made the purchase from them then, under the same Act, the contract of sale is with them and they are legally obliged to rectify the matter.
Hope this helps.