I think people are still missing the point - the people who have to pay have been fleeced, not the OP.
There's no reason why dowie should go out of his way to get a lower price at all. If the idiots are so bothered/guilty they could have arranged it themselves.
Out of interest, have any of them apologised?
in my experience, in situations like this, when the OP asks his flatmate for the money, his flatmate will go "hahahaha, no" and the OP will be out of pocket by £370
) he's gonna laugh in your face!