I think Noel Hayes has come up with the perfect formula here, as you say, take the airports where the big boys cannot touch you.
BLK will always be a success and other routes such as BFS and GLO and JER are not possible to service by any other carrier on that scale. The BFS based airlines are all A320/B737 operators who wouldn't be able to operate a decent frequency compared to demand.
The only routes I can see M2 vulnerable on at the moment are BHD (where BE have a huge presence) and LBA which is may be in the scope of BE for further expansion. Unless the an airline wants to launch 4x daily to BLK at £15 a head, I cannot see M2 worrying too much over the next 12 months and I think their expansion plans support this.
Congrats to M2 and the management who seem to have discovered a winning formula!