Simon suggested the same for Flyglobespans engineering.
Having worked for a very large UK carrier with it's own engineering and now GSM with contracted staff, I can see no discernable difference between the two products.
Monarch were contracted to do my old carriers 330 mtce at MAN. And, yes, they were very good, but no better than anyone else. An engineer with a licence wants to keep it, and that means working to the best of their ability.
Loyalty to their own company means diddly when it comes down to safety.