LHR routes are the only flights CO currently "guarantees" flat-beds in BF (since June). I use the quotes as there have been a handful of flights where that has not occurred, but I know of none recently.

There are virtually no bad seats in any of the BF configurations, as the seats are comfortable with ample space to spread out, AVOD, and of course, the lie-flat capability. With that said, the bulkhead seats are popular for the extra storage space under the ottoman (and extra foot space on the ottoman itself). As was discussed above, the center seats on the 772s are also popular as you have the freedom to leave your seat at any time without disturbing another passenger.