Welcome to Flyertalk and welcome to the BA Forum.
You may want to have a read of this thread and its wiki, which refers to downgrading and the Mennens rule.
https://www.flyertalk.com/forum/brit...uk261-apr.html
But yes, at 8 weeks just go to CEDR and claim Mennens that way. At the moment the Customer Service facilities of BA have deteriorated very badly due to a botched implementation of Salesforce and the loss of key staff.