Yes I remember EI-BTR operating for British Midland in the 80s. I have a photo of it there, taken from the rooftop terrace. It's not a particularly good photo, tho - taken by me as a child. But you can clearly see the reg and MME's terminal.
And I flew the DC-9 a few times. Yes it will be sad to see them go. But it's their airline, they need to run it as they see fit, and not just to please enthusiasts.
I much prefer KLM/Amsterdam for my connections anyway.