One exists in Scotland I don't know where, probably too embarrassed to show it!
There was a casing from the B.20 at Hillington in Glasgow under the care of the RRHT there many years ago, but I don't know if it is still there.
He refused to go into the upper turret which was called, the "Botha Turret."
The dreaded FN.7A - a terrible thing fitted to the Botha and Saro Lerwick that gunners didn't like because of its awkward shape, the Manchester didn't like it either, when turned at speed it upset the aerodynamics and caused severe vibration of the rudders and central fin, which caused its fabric covering to tear and in one trial its disintegration (!). It was initially intended that the Manchester had an FN.21A under belly turret and no top turret, when that didn't work out the FN.7A was fitted.