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
Thanks for that. I already tried that, and for some very strange reason the flights from LHR-PHL have
zero CW reward seats available on a Friday (the day I am travelling) on any day from now until Dec 24th
