The RRP for this SanDisk 4GB, class 4 microSD card is, according to Play, £29.99. But Play has knocked a whopping 86% off, meaning you can grab yourself some SanDisk microSD action for a significantly more affordable £3.99, delivered.
These guys appear to be quite popular (understandably). At the time of writing, the estimated dispatch time is 1-2 weeks.
(Thanks to Szpakos at HUKD)