

https://en.wikipedia.org/wiki/OTO_Melara_76_mm
When we built the Peacock Class of patrol vessels to serve in Hong Kong they were built to carry the 76mm oto melara. Now with the discussions of the Enhanced role for the River II OPV and the Fictional sorry future light Frigate program the Oto Melara has been put forward as a possible armament. Since Royal Navy have already operated it it's interesting they have not put it forward again for service on any vessel built after the Peacocks.
I don't see any requirement for the 76mm gun in the Royal Navy. The 4.5 came back on the Type 22/III and the Type 23, 26 & Type 45 for the role of Naval Gunfire Support a role the 76mm is to light to properly fulfill. The 5inch gun provides a better support weapon and complicating naval gunnery by having to duplicate training and support for 2 different main weapons only adds complication and expense.
HMS Starling