c) I would now look at the new odds of the other team and the draw. I would now back whichever of those two is value against my prices. If both were now value, I would back them both.

What I would never do is (b). If you blindly green up simply by laying a shorter price than the one at which you backed, then you could well be effectively having a good-value bet on one of the other two possibilities, but a bad-value bet on the remaining one.