From my cursory flick through, I'd say that the adaptions for British and Commonwealth Usage comprise replacing the work tube with valve, and 110 VAC / 60 Hz with 240 VAC / 50 Hz.
I did think that maybe they'd replaced the 'z' in words with 's' but that's not the case.
Seems they only did 2/3 rds of the job ;-)
Martin
M0HKG - Martin