Dave (#1) and Nervous SLF (#7),
There were Mk.XVI FBs in India from early 1944; they came out to re-equip the four RAF Vultee Vengeance squadrons which had been withdrawn from operational service that summer (there was a six-month delay in the Mossie introduction as they started falling to bits, sometimes in mid-air to the consternation of the occupants).
Never heard of the "tsetse" Mossie until now. As for a 3.7 (AA ?) gun, I would've thought that a bit much. But the Americans had a B-25 ("Mitchell") with a 75mm cannon with the barrel between the Nav's legs (so I was told).
The spent cases polished up nicely: they were in demand as tocsins and in later life some became umbrella stands.
Danny42C.