I was watching the vlog for the show on youtube. It seemed that there were just as many American actors in the cast as there were British.
I thought that the trade thing was an eye for an eye type of deal. In other words, one British actor for one American actor and so on and so forth. I never realized that you could do more then one actor.
"If you try to shag my husband while I am still alive, I will shove the art of motorcycle maintenance up your rancid little Cu**. That's a good dear"
Tom Stoppard's Rock N Roll