If Concorde does go number one, then it'll affect the landing times by what, one minute. If its that much of an emergency (shortage) even Concorde can declare a mayday/pan and then get the priority anyway, just like anyone else. And, having no dealings with Concorde procedures, I believe that if it goes number one, then the BA a/c that was first then picks up Concorde's delay.
PS. I have seen it holding at OCK before.