Rude surprise (to me, at least): after paying extra for premium economy for LHR to BOS, I had to pay still more to choose seats ($65 each)! As even the premium economy section on the 777 has a 2-4-2 arrangement, waiting until the day of the flight could have left us in the middle of a 4-seat row in "premium."
I expect this in a budget airline, but I guess the flag carriers have joined the greedy crowd.
So beware -- the price you see online is lower than the price you are likely to pay.

Being able to select your seats by paying a fee is not new and it applies to many airlines. It is an extra, so it is not included in the price online. Most do not choose to pay extra for seat selection and the price paid is the one advertised.

You can actually pick your seats 24 hours before -It's the same for Biz class too! It's not new ( or usual) but their prices are steep....

Flying back from Buenos Aires on BA I paid £40 pp a few days before as seats were getting booked up and it was a long flight. Tried to print of our boarding passes and our seats had been changed. Queued for ages at check in and was about to express my displeasure but the attendant took the wind out of my sails by saying "so sorry we are overbooked......we have had to upgrade you" bloody BA!! Such a pain!

What I failed to mention and that Smeagol addressed is that you can select seats 24 hours in advance free of any charges. This seems to be what the majority of passengers do. I 've done this for years and have always gotten my preference. If there is an important reason for a particular seat then book seat when booking flight but it is an extra expense. Long gone are the days when airlines cater to your every whim without charges.

I think you made the smart choice. I've waited until online check in opened and was fine, but not when the possibility of being stuck in the dreaded middle section was there. I don't like it, but it is what it is.

This is the way BA rewards their status passengers who frequently don't book until later than the rest of us who just fly occasionally for vacation.

Enjoy your trip!