Hi, we travelled BA/Qantas late last year (2006) and I have to say BA was a dream and Qantas was hell. I would definately travel BA again
DS was 5 months on the way to Oz and the bassinet was confirmed on all flight sectors there and back before we left London.
When it comes to the airlines, I guess it all depends on the crew on each flight. Have not flown Singapore Airlines but have heard many glowing reports.
We stopped over in Singapore on the way to Oz and then Bangkok on the way back. The break was wonderful and adjusting to the new time zone on the way there was very handy. Singaporians are very warm and welcoming and just LOVE children.
In regards to booking before your baby is born, you can go ahead and book your flights and the baby's name can be added later when you know. I used to work as a travel consultant so you can take my word for it. An airline will allow you to add an infant name at any time as an infant does not have a seat. But be aware that you can't change the name on the ticket once it has been paid for (even if just a deposit has been paid).
Check out this website for information on each airline including facilities available on board, seating layouts, baggage information, links to airline websites etc seat guru
DS travelled really well - slept most of the time. If you need to stretch your legs with bub while they are awake - go for a walk into the main galley area. People come and go all the time asking for drinks and extra food and just love to have a chat to bub. The crew usually love having a chat as well. It was great for me as I travelled back to London from Oz on my own and having someone to chat to was a relief (guy sitting beside me was very anti babies
Oh and it's Gulf Air with the onboard Sky Nanny service which is FREE! check this out
Hope this helps!