According to the website search tool there is availability for PE tomorrow on the BA39 but when you go to do it online, still getting a contact your TA message ( passed T-24)
Just phoned BA, there is no availability so it's a back of the bus experience again for me on a flight where there is no extra legroom seats in economy (my beloved 29a appears to be a PE seat)
Agent on the phone was very helpful but no joy