This deal was posted over a month ago, but I went into my Local PoundLand (Colchester) yesterday and they had them in stock, but a who different set of designs to last time. I got a fire one and a goldfish one.
Hopefully it's nationwide.
Will scan the picture of the designs.
they're 36.5cm x 27.5cm, they were just a smidge too small to entirely cover my 17" laptop, but might cover some, and are perfect for 15.4. and also Would fit nicely on top of an xbox 360 (provided you cut vent holes) so would be a dirt cheap way to customise.