If the retailer is a UK firm, then the current version of the Sale of Goods Act applies, in its entirety. This includes purchases via the net.
The contract is between you and the retailer, not the manufacturer. So in the first instance, inform the retailer and take it from there. Many retailers will be members of their own 'trade' Code of Practice, e.g. the Alliance for Electronic Business, which can all help.
Don't forget that, if you hit serious probs, the credit card people are also a party to the contract, so they may also be able to assist by applying pressure. (I think that's for purchases exceeding £100). HTH.