Welcome to NCL- BA's poor relation. You will see that MAN, EDI, GLA and even INV have better timed connections than NCL. It's either run like hell to make the early one, or doss around the terraces for 5 hours waiting for the next one.
You have my sympathies- I have been caught in this trap before too, except I was connecting from Continental arriving at 6:40am in the south terminal. BA were actually very nice, and held the flight for me... I wasn't throwing away another sector though. Not sure how they'd react to this. Best of British luck to you...