Andrew,
I had precisely the same code from time to time with the completely standard GDI. It's just the downstream lambda sensor indicating low cat efficiency. Nothing to worry about. It usually happens in cold weather or if the car has idled for too long and the cat has not warmed up. I get it now with about the same frequency with my free-flow manifold and new 200-cell cat. As long as the car gets fully warmed up before its MOT it should pass.
