Folks,
Re. fuel remaining overhead EGLL of 8+, what's the problem, that would probably get you to EGKK or EGSS as a full alternate with the B787, based on my B767 time.
Arriving over EGLL with less than 10 in a B747-400 is not unknown, and with an alternate criteria of around 400/1600 (for many airlines even less) it can be quite inclement weather before an alternate in required, but that all depends on your UK CAA Ops. Spec. for your operation.
Contrary to "popular belief" not all airlines carry alternates for all flights, even in Europe.
Tootle pip!!