ORIGINAL: rtrapasso
The Brits WERE bombing from "masthead height" from the beginning of the Pacific war, but they hadn't developed the "skip" technique, i AFAIK they didn't have special bombs... their results weren't nearly as good as the later "skip" technique. i expect they had a lot of problems with the bombers being damaged with their own bombs... i don't recall the exact details, but i am pretty sure they pretty much abandoned it due to high casualties.
The RAF employed masthead attacks against German merchant shipping in the English Channel from 1940 onwards. If anything, their doctrine encouraged such an aggressive approach. Not aware of self-damage from bombs being a major problem, but Blenheims were suffering anything up to 25% casualties from AA fire, Luftwaffe fighter cover, and the hazards of operating at that level - eg hitting masts, towed barrage balloons, or just the Oggin itself. Coastal Command also employed very low level attacks from 1939 vs U-boats - these latter attacks did suffer some self-damage due to poorly designed ASW bombs skipping and exploding behind the aircraft.
The RAF eventually solved the casualty problems with faster, better aircraft (Beaufighters and Mossies), carrying a lot more firepower (a Beau with 4xHispano and 6x.303 arguably the match of the B-25 gunships) to suppress flak on the run-in, adding rockets and torps into the mix, and using massed wings of 30+ aircraft to mob a convoy. By the time such toys and tactics became available, suspect pretty limited trade available in the SEAC area out east; Beaus did a good enough job anyway, in penny packets, vs any small craft they chanced upon. Put bluntly, the British area of ops in the East had a coastline running roughly at right angles to the front-line, while in the SW Pacific (and the English Channel) it more often approximated to perpendicular, giving more targets and easier reach.