Barrie,
Sorry for my late reply, I went to the UK last week. Interesting that 22 and 31 are identical in this respect as well. The front wheel boxes on 31 were pop-riveted to the frame when I bought the car, I do suspect that they might have been screwed with some self tapping screws originally. Could I ask how they are attached on 22?
I did get some nickel plated screws with 31 when I bought the car, I strongly suspect they were used for this application.
I guess that AC didn’t spend too much time to develop the first LHD Ace they manufactured, since the battery is in a rather awkward position. Before I changed to screws I had to dismantle both the steering box as well as the carburettors to get the battery out, or a 5 minute job exactly!
Finally I think it would be very interesting to gather some early cars and compare different solutions and maybe to some extent get a grip of when the factory did change certain details?
Jonas