I tried my hand with this too for the LHR-BLQ flight, arguing that the airport knew it was going to have to close 2 days prior to the flight leaving - BA knew it was happening yet failed to tell passengers/make alternative arrangements. Yet BA are absolutely adamant that the original delay/diversion to my flight was completely out of their control...

According to BA it doesn’t have a leg to stand on but I think it does, but I can’t be bothered fighting it. Got to BLQ 5 hours late that day, and I would have cancelled if I knew it was going to happen. No apology or we could do better etc either. All in all poorly dealt with.

If if I was in your boat I’d dig up the articles that say they knew BLQ was going to be closed and try my hand at CEDR, best of luck.