Going loco. You're completely wrong to describe MAN777 as displaying spotters logic. I'd do exactly the same thing, for one reason and one reason only....
The economy of regional Britain gains immeasurably from having connections to Singapore, Chicago, Atlanta etc. This is probably not apparent to someone from Dorset.
Many many overseas firms locate in Greater Manchester, and the West Midlands also, precisely because you can get to and from them from a wide variety of places.
I would never use a connection via another EU airport (including LHR), if a long-haul connection from MAN wasn't available first. Thankfully, it's never happened yet.