I have a question regarding MFU specifically to upgrade from WT -> WTP.

I have read the Ultimate BA guide thread and it states that I can only use MFU if I book in Y B or H in WT in order to MFU to WTP.

Assuming I am booking from the BA website is there an easy way to tell before I complete my booking, that the ticket I am about to buy is eligible for MFU?

Thanks in advance

rk164