There appears to be an itsy bitsy problem with BA reward flights at the moment.
Be very careful, I looked at a long haul MFU (buy the class below and upgrade with miles) and the price was a lot more expensive than buying the class above for cash. I'm talking about over £1K more.
The reason for this was no reward seats whatsoever on the routing, from now until early August next year.
Others, on other fora are reporting lack of seats, so be very careful with BA presently.