Was just about to put it in the bin, when I thought I would see if I could find the receipt. I did and it was still under warranty. It was (5 years).
Went on SanDisk's website and filled in an RMA form, assuming that they would approve it and send me a replacement. Instead I was emailed a UPS label, and they asked for it to be sent back to the Czech Republic.
I just had a look at the tracking details - it has so far travelled to London by car, flown to France, then to Frankfurt, then to Nuremberg, and I assume from there it will be flown to the CR.
The stick cost £6... Mad!