To be fair to the U.S controllers - many have very difficult shift hours, some of which leave just a few hours for sleep in-between. Blame the F.A.A not the controllers.
I've never heard of a U.K ATC sleeping on the job. Not yet anyway

All the ones I speak to are pretty clued up. I think we have the best ATC in the world here in the U.K.
Any chance of direct ORTAC?
Adam