At the moment rows 23 and 24 are all blocked out, and a bit of 25 too. But that is it on the service, very few other seats taken on a low status route. CE on the other hand is filling up past the first exit area and is currently up to and including row 10. In my experience, and subject to staffing issues, BA will want to push the curtain back, there is no realistic chance of getting that front exit row again. And that factor, plus the A321, has led to your difficulties here. 24D isn't really helpful, so perhaps if you go to say row 33 you may get an empty seat next to you, right now 24C is taken.