PM replied to.
Okay, the panel from XE673 is now in my posession, many thanks to James & Duncan. I have found out that it is an access panel that fits on the port fuselage, under the wing fillet.
I have received a picture from the gentleman who owns Miss Demeanour, the rather pretty Hunter, which shows the location, it is the panel hidden under the wing fillet, in the foreground of the picture, you can see the bottom third of the panel. When I work out how to upload pictures from the laptop, I will post it here.