complicated... the cheque coming off the card (I think) waives your protection under the consumer credit act. I can't see why it would because it's the process of providing credit that creates the legislative protection. However, the process of paying by cheque rather than through the credit networks means that the card issuer has no protection from the merchant, with whom they usually deal with directly and can therefore identify.
All this said, I think I'm right in saying that the encashment of a cheque issued in full or part payment for a good consititutes full acceptance of a contract of sale and therefore failure to provide goods as described under the Sales of Goods Act would give you good grounds to sue.