Operating Emb 145's into LHR is commercial suicide. bmi have already proved that... So the reality of a small business being able to absorb those sort of losses just doesn't make sense to me.
I might be wrong, but unless Granite refleeted with bigger aircraft asap, then I don't see how they'd make it pay. I doubt whether Virgin would cover the cost for them.
Refleeting isn't exactly the cheapest thing in the world.