SeatGuru is useful for the comments on various seats but it is not always correct. And you cannot reserve your seats there.
I saw your previous post regarding your frustration with BA seating policies, but still do not understand what problem you are having. If you are going to pay to select your seats ahead of time, you just go into Manage My Booking on the website and do it. You can only do this after the flight has been ticketed, which may not be right away if you book over the phone. But if you book online, you can do it right away. I just did that yesterday, reserving two Business Class seats with our miles and then paying to select the exact seats we want, on the upper deck of a 747.
If no seats are indicated on the seating chart as available to reserve, then it is likely some of the most desireable seats are being held back for high-status Executive Club members, and the others have already been taken. I noticed this yesterday when I went to choose our upper deck seats. Although it was the first day (and hour) the flight was available to book (this will be next May), only about half the seats on the upper deck were open to me, as we are lowly Blue members. However, the exact seats we like were available, and I booked them. Now there are even fewer left for non-status fliers.
Calling BA can be a pain, as the wait times can be long. But once you get through, they should be helpful (although at certain times the Customer Service line is a call center in India and they may not be able to help you).
FWIW, we like Row 11, aisle and window seats, on the BA 777 in Business Class. But we like the 747 planes more, and are glad to see them return to Seattle service.
