LiveryMan
You talk total tosh, both on the reason for BA continuing and that an engine failure on a four engine aircraft means a diversion.
I can only speak for the 747, not other quads, but as long as you can satisfy the flight continuation policy (suitable alternates en route, high terrain, 2nd engine failure at critical point, know cause of failureand whether the engine is damaged and health of other engines etc) it is permitted and positively encouraged to continue.
FWIW the BA LAX crew ended up in Manchester but could have gone to heathrow, and the FAA had to formally apologise to BA for their handling of that incident.
LD