Thank you very much WT1 for the information on William Bigger, it's always nice to be able to link these things. And to Backroads, the Canada sheet of stamps did, if I remember, feature on one of my earlier topics and most likely on some by others. I have this sheet, and the Seagram's Whisky sheet with folder. Unlike with the 1937 Coronation, I have not seen that many covers bearing Visit labels; maybe just that I have not seen many or that they were not used so much on envelopes?
For Bujutsu, I have put the images below up on an earlier thread but in case you have not seen them before:

These are of course the UK 1937 Coronation cinderellas but overprinted for the 1939 Visit. There are also the USA version (both in all three colours as originally issued in the UK):

These have been seen elsewhere by an eminent Royal Visit collector but otherwise seem to be very rare. Chris Wren