Unfortunately with BA you cannot see the seat map until after you have booked so on the o/b there
Yes you can. During the booking process I'm pretty much certain there is an button on the form that takes you to somewhere where you can choose your seats.... before finalising your booking.
Just like this, I visited ba.com, didn't login to my account, just started going through the standard booking process....
Lady Groundhog, bronze card, can get a look 7 days before departure. Does the 'pre bookable' allocation change, is it worth checking every day or should we wait till minus seven days?
Yes it changes... fewer seats become available for you to choose from as the aircraft fills up...