I have now been trying to find flights where I can use the voucher. I thought that all I had to do was find Club Class that was available and select to use the voucher. I am confident that I read a seat in the lower class doesn't have to be available.
It seems that it's not so easy.
Off I go to avios.com. Even though there are plenty of return flights BHD-LHR-DXB January 2018, and there are Club Class seats (and Economy seats) available, nothing is highlighted in Green (as the message asks me to click on). It looks like the Premium Economy (WT+) seats aren't available to book with Avios - so there's no WT+ to upgrade from.
Have I got this wrong? Is this a ba or Avios query?