Originally Posted by
divenow67
With regards to your second point, I have just MFU'd two WT+ LHR-BOS-LHR seats.
To achieve this I merely looked up the above route in the 'Book With Avios' Flight Search, saw the availability in Club World I required then quickly booked two WT+ seats on BA.com and also managed to immediately MFU them on BA.com too
Best of luck!
This is the correct approach, but you can also MFU during the booking phase by selecting "Book with cash, upgrade with Avios" in the Payment Type drop-down.