I have therefore decided to do a backup of the files from the SD card to my PC, reformat the SD card, put everything back onto it, and then upgrade it.
Fingers crossed that it all works.
*Next time around I'm very tempted to buy the phone outright for myself, meaning I get the update when the manufacturer releases it, not when Orange have finished putting their crap on it. Not that Orange seem to put a lot of crap onto the Desire, that I've noticed. If it wasn't for the phone insurance, and a new Desire costing £400 new, I'd have done that last time around.
