That's an aftermarket Lockheed booster. You can see the mounting holes from the original Girling booster. I'm not familiar enough with Plus 2s to say what boosters they had originally, I suspect all original boosters were Girling units, though.
I'm not aware of any Europas that had a booster in the front. I know TCs pretty well, though I am constantly learning new things about them, I am far less familiar with S2s and S1s. It think I remember many years ago I read about a guy who put a Japanese truck M/C complete with booster on a Europa, I wouldn't trust that memory. As far as original setups go, it seems highly unlikely they would run a vacuum line all the way to the front of the car.