"Argue until the cows come home, the policy is correct, the CAA apparently agrees, the FAA has got other drums to bang as well and is definitely not to be trusted. The policy still applies in BA and is supported by the very people who follow it"
This would appear to bear out your comment, bullshot.
Why is the 'apparent agreement' of the CAA any more to be accepted than the view of the FAA which, it is being alleged, is 'definitely not to be trusted'?
The fact that there has been such a difference in views means that this is far from a cut and dried issue.
The redundancy of 747-400 systems is totally irrelevant to this issue; this was a 4-engined aeroplane which lost 25% of its available thrust on take-off. The issue at stake is whether, as a general concept, it is an acceptably low degree of risk to plan to fly the remaininder of the flight to the original destination with fare paying passengers on board over such a lengthy sector.