How would you "half-burn" AVPIN? The stuff is sheer angriness in a bottle!
The PR.9 (but not the other Canberras, they used cordite cartridges) used it too, as did the Lightning, Javelin and soem Hunters. I don't know why a Canberra would bother with it - it's foul stuff and has all sorts of problems, even worse than hydrazine. It was just about justifiable for a rapid reponse interceptor scramble in the '50s, but why for the PR.9s?
Sadly the shortage of AVPIN these days is likely to stop the privately- owned Lightnings from running again 8-(