Thanks, but I can't find any reference to a "Gold Priority Reward" anywhere on the website, even when signed in. How does one find that option?

Secondly, as others predicted, no seats are available in Club on LHR-NBO between Dec 22 and 24, when we need to meet our tour. Completely pointless trying to use Avios, once again. Aside from "no availability", the website's favorite phrase seems to be "There was a problem with your request, please try again later."

And even if I was able to upgrade the IAD-LHR leg, it looks like I'd have to make two separate bookings, since no seats show for LHR-NBO, and the only option then is to start a new search. Doesn't appear to be a way to upgrade one leg and stay in WTP for the other.

Looks like the back of the bus again. I really hate BA's website. Thanks for the replies.