Dunno where'd be cheapest in UK.
I'm on my second Lexar Compact Flash card, 'High Speed Digital Film' 12x (1.8MB/sec) which has a warranty as long as owned by original purchaser.
The first completely froze up, losing one folder of images and locking another. There was also a folder of various files. Fortunately all the stuff had already gone to the PC.
Lexar sent me a new card which is working OK. Only complaints - bit slow in handling and about three quid at my expense to post & insure.
Hope they weren't too offended by the folder of various files which was a compilation of laddish jokes/pics/videos given to me by an old buddy I met BKK-LHR