Yes! Lots and lots and lots of folks! You do need to get a decision that is final, and then you can go to CEDR. If they ignore you - then after eight weeks crack on.
It's very simple online to complete. You don't write war & peace - just the date, the reason for cancellation / long delay which you believe wasn't "exceptional" and then leave it to CEDR to take to BA for explanation. It's not for you to prove, it's for BA to prove in their response. Use the main website and don't use a middle man / agent.
Dispute Resolution, Conflict Management & Mediation Services - CEDR
Maybe have a read through the first post or two here, and the last few posts
The 2021/22 BA compensation thread: Your guide to Regulation EC261/2004 - FlyerTalk Forums