As someone who has been making these trips since the original ex LIS days, my compliments to the authors of the thread !

One thing I would comment on is the length of the permitted stopover in London. In the good old days the stopovers were unlimited in duration and not particularly painful from a cost perspective. This did enable the short haul first sector to be taken months ahead of the longhaul trip. BA has, as noted above, gradually limited the stopover duration and many fares now have a max of 10 days and a hefty stopover fee.

Even the 10 days would be potentially useful, but it has also to be borne in mind that any UK stopover of 24 hours or more requires UK APD to be paid for the noward longhaul sector. Since the fare (at least in CW) often has a €200 stopover fee, a stopover of more than 24 hours can add nearly £400 to an otherwise bargain basement ticket.

This also means that saving the last 'unused' sector for a future trip has also become a lot less attractive. With a €200 stopover fee, £26 APD and a possible change fee if the date of the next trip is uncertain, using the last sector for a future trip is rarely a particularly attractive option.