Dodotori, monsieur, Bien Fait.
Aaah. Beautiful, you see, this is why I wish I had actually studied comp-sci; then I might be able to figure out stuff like this!
It's not too strong to say that I love your solution!
Just tested it and it's working perfectly. (Had to use a letter accesskey because chromium uses the numbers to jump tabs.) I'll post a different solution in a second but I'm saving/ re-using your method to see if I can create other accesskeys for things that I'd given up on (eg wrap plugin for columns, buttons and centralised headers).
Thank you again. You've already got some sort of FOSS-contributor good karma but if there's any way I can buy-you-a-coffee or something then please do tell me.