At times, but by 1942/43 the British were using mostly AP and incendiary bullets and had stopped using the Infantry bullets. Even during the BoB only about 37% of the ammo was "infantry" ammo.The RAF had warehouses full of .303, and whatever reason(s) got considered (rate of fire, density of pattern, etc) that had to be Hewge.
Fortunately, the US signed on to the .50 caliber which gained global air superiority.
British couldn't get the cowl guns to work in the early Tomahawks. Lt. Hubert Zemke was writing reports that June and July of 1941 about British complaints about the cowl guns suffering endless trouble.I'd amend your statement to read "Fortunately, the US signed onto the .50 caliber and persisted to resolve operational problems with wing installations of the weapon so that it could gain global air superiority."
There's no way the RAF could have used the .50 cal mounted in fighter aircraft wings in 1939 or 1940. Weapon production wasn't sufficient, and wing-mounted installations were prone to jams (a problem that continued thru to the second half of 1942).