Some more for your collection, Mick. These were taken from my copy of David Fletcher's engrossing 'British Battle tanks: American-made World War 11 tanks'. The Firefly sports a .30cal Browning on the cupola; but since Fireflies had no bow MG as secondary armament, and so makes sense to have one on the cupola.

It also makes economic and practical sense to use .30cal rounds, as Britain was awash with them. Britain also made .55 cal rounds for the Boys Anti-tank rifle, which wouldn't fit the Browning M2. That said, I believe the Royal Ordnance factory at Spennymoor, produced .50 cal ammo, but it was supplied mostly to meet the demands of US B17 squadrons, from what I've read.

Firefly with 30cal Browning (above)
Here's a British Sherman (75mm) also sporting the Browning .30cal, as is the Firefly immediately behind it.

It's a curious thing, that whenever we see American Shermans in films and pics, the turret-mounted .50 is often a prominent feature. I'm just wondering whether Brits preferred to use co-axial guns for strafing?
Just an idea.
Incidentally, I started a thread a couple of years back of defensive weapons carried by tankers (pistols and submachine guns). Close up, these weapons could be easier to use (through pistol ports and hatches, etc.,)
that fixed mounted turret guns- even those with Brad Pitt pulling the trigger

..
In fact, I've fired most of them (Tokarev, Walther P38, PPK, Enfield No.2 Mk 1, Browning 1911, Luger etc..), but not the Greasegun (US tankers), and Schmeisser MP40. My lad has all of these (fully operational), except the submgs. But, for obvious reasons, submachine guns are almost impossible to get hold of in Switzerland (where I go to shoot), unless they are chambered for .22, and modded to semi-auto only status.
"Get your facts first, and then you can distort them as much as you please"- Mark Twain.