Originally Posted by
KevinM2
OK, thanks for that. It was going to be WT to WT+ (no club seats available, unfortunately

).
Guess I'll have to have a re-think...
IIRC to upgrade from WT to WT+ requires pretty much a full-fare to be purchased in Y
Another thought on checking MFU ability is to look for your flight (or date range) at the excellent tool ba.com has for checking BA Miles redemption availability. I believe the MFU stock per flight comes out of the same class as a straight BA Miles redemption so you would be able to see over a monthly range at at a time what days you could use MFU.
If I'm wrong on the above someone helpful will no doubt correct me