This is the problem dealing with a supplier not based in the UK.
Sales from Pixmania are governed by French Law. Even if French Law provides the same protection as English Law, it would necessitate you bringing the action in a French Court. This is not a route one would be likely to go down for a graphic card.
On the Pixmania site they state: "During the first year of warranty, if you experience any problems with the product you contact the manufacturer's after-sales service".