’Twas ever thus!
I think we started warning airlines with at least 6 months to go to the change, and this change was originally requested by the airline community too!
Off the top of my head, it was raised at, and briefing packs I wrote were sent out to, the LHR FLOPSC, Heathrow airline station managers, the NERL ops group, the NATS SPA, BALPA, UK Flight Safety Committee, and IATA UK. I spent days at Waterside and T5, and Virgin crew report centre, and shotgun emailed any airline.
There’s only so much one can do. There was certainly no lack of information sent out!