SPOILER ALERT
If I've got them all correct, the letter changes are in 11a, 13a, 14a, 21a, 23a, 2d, 15d, 18d, 19d and 23d.
But if that is right, I'm not sure what it adds.
Harumph.
On a happier note, Azed gave me a VHC this month so I'm on top of the world! Perhaps one day the bookplate will be mine...