Picked one of these up today @ B&Q Gillingham, Masterplug weatherproof twin socket on a spike c/w 10m of orange cable and 13A plug. Seems to be an end of line product, so may be nationwide, 10m cable version no longer on their website.
They had an end bin full of them all reduced to £2.98 down from previously reduced price of £12.98, not sure what the original price was.
The only one I could find on the website is the 15metre cable version in the link, this is still listed @ £24.98. But other than the cable length it is exactly the same.