Here's what I found over the weekend: http://www.jessops.com/shop.cfm?product=JESDLCDSP

They're in stock in Jessops shops, too.

I've not actually /tried/ one yet, but I do know:

a) £3.99 for 3
b) They are only slightly too big for the 770 screen, hence they do fit (with a bit of cutting down)
c) They are obviously OK for touch screens are they're sold as being suitable for PDAs and the touchscreens on the back of more modern digital cameras
d) I think there'll be no problems when replacing a worn-out protector, as why would one get 3 to each pack otherwise? In other words, I don't think they'll weld themselves irrevocably to the screen ...

I'll update this thread when I've actually applied one ...

Jaycee