I finally got the chance to use bmi for a long haul trip.
I managed to get a single LH ticket that will get me from Bristol to Brisbane, using bmi to get me to and from Frankfurt, Lufthansa between Frankfurt and Bangkok, and Thai from Bangkok to Brisbane. It wasn't the cheapest flight to Oz I've ever booked, but I'm so glad not to be starting or ending in London.
I'm planning to check-in a little bit earlier than usual, just in case the cleverness of using an LH ticket on BM doesn't work as planned. If it does, then I lines I'll just spend a bit longer in the lounge.