And just to note the available workarounds from squawk and me, for anyone who hasn't seen them in the bugs and glitches thread (https://www.flyertalk.com/forum/brit...l#post33950485):

1. Go to your BAEC home page (https://www.britishairways.com/trave...club/_gf/en_gb) and use the sidebar to search. Selecting an old-style voucher and typing in a long-haul destination should still bring up all four classes in the drop-down classes list, like it does if there is no voucher or if a new-style voucher is selected.
2. Go to the main Avios search page (https://www.britishairways.com/trave...club/_gf/en_gb), and make sure you select "Business" from the three-class drop-down list that shows when an old-style voucher is selected. The search results page should show you columns for Premium Economy, Business and First, even though you couldn't directly select First from the drop-down menu.
3. If all else fails, using the "Change" function after seeing search results should show you a four-class drop-down list.