I have as you have stated used the plan and book tool. At present I have a PNR confirmation # although I have not paid for this booking. When I log into my BAEC account I can see my seat assignments and make changes. By using checkmytrip.com I can also see the locators for the other OW airlines in this RTW.

Have you called BA to give them your credit card number?

If you're using the online tool, I'm not aware that you can put a RTW itinerary on hold, get a PNR and not pay for it immediately (by inputting a credit card number) unless you book via BA (which you are). Although I have no personal experience of it, I think somewhere in the FAQs for the online tool, it talks about providing a credit card number when you book, unless it is being ticketed by BA, in which case you have to call a BA office and give them your card details (specifically "For bookings issued by British Airways you must contact your local British Airways office to pay and complete your booking."). If you haven't done that already (and presumably it's not going to 'ticket' until you do) you may want to do so before all your segments auto-cancel.

This has changed. QF opened up lots of A availability a couple of weeks ago, at least for the SYD-LHR route. I flew SYD-LHR on the A380 on my AONE6, and had a great flight...