Business Air used to fly Belfast-Manchester with the saab 340, although it didn't last long from what I read. G-GNTZ is the registration on the photo I have, mind you I think I saw that same reg on a Logonair saab 340 recently. Thieir flight numbers started with II and looking back in the timetables I have they had about 4 a day on this route
Another one from years back was Air Belfast who used to have a 1-11 flying from Belfast to London Stansted in about the same period. Didn't last long either. Their flight numbers started with 7L
Hope this helps