I had heard / read (sorry don't remember where) that they were considering the latest incarnation of the OTO Melara 76mm which is on a number of European ships.
Seems the T26 won't need to be in the game as it has been downgraded and assigned to Anti-Submarine warfare:
http://www.thinkdefence.co.uk/2015/11/the-type-31-frigate/
The above link also shows just how "pie in the sky" all RN future vessels are... unfortunately.