Originally Posted by
NotForLeisure
On the sidebar on the left on the executive club homepage, if you select book with cash and upgrade with avios, you are only able to select Economy as the travel class once you have entered the departure airport.
On many of the booking pages, the page will only work properly if you wait for the airport options to be presented to you (after typing a few relevant letters) and positively select one of the options on offer, for both depature and arrival airports. Irritating, but I think that's the price of a dumbed-down internet.
If you've done that for both airports, can you then select one of the other cabins?