The big problem has been that due to the recession, some of Bombardier's subcontractors have been unable to provide the sub-systems required for the 377/5s. So only a handful had been delivered in time for the start of the new service on March 22nd.
Since the 377/5s weren't ready, an even more complicated cascade than the one planned was arranged. Southern (which owns the 377/5s anyway and is due to sublease them to FCC) subleased its own green 377s for the duration of the shortfall, and London Midland is leasing 350s to Southern to do the work of the missing green 377s.
As the 377/5 s ranks swell (and it's hoped that one 377/5 will be delivered per week), the green 377s will return to Southern, and LM will get its 350s back.
Phew
