I submitted an EU261 claim to BA in September 2023, after lots of debating with BA (they blamed weather when it was an operational issue within their control) I finally submitted a case to CEDR on 15th February 2024. The process was easy and really good - I received a full settlement from BA on 20th March 2024. I think having lots of evidence in support of my claim and knowing what I was and wasn't entited to made a difference. I'd wait the 8 weeks as suggested and go to CEDR.