Right, I've finally used these patches. I've not had a blister to test them on since they arrived due to not getting out as much as I'd have liked and converting to lighter footwear.
But, recently I've worn through the heel lining on a pair of hiking shoes have and these, in turn, have started eating sock heels so i put the patches over the damaged area in the shoe heels and this has stopped the sock eating issue. The patches have been on for several months now and show no sign of peeling off or of earing through.
Not strictly what the patches were designed for but as close as I'll get (I hope) in the forseeable future.