Never heard of it, but then I'm way out of touch with light aviation. I've just heard that de Havilland have launched a new aircraft, Tiger Moth or something .....
Yes I know - it was just the angle of the photo, with the edge of the bob weight visible, made it look smaller than a Blenheim, which is why I had doubts.
Anyway, try this one. Apologies for the grain/pixelation, but I think it shouldn't take too long to solve.
Matches the clues very well Jim.
It's grey in parts (most of it in fact!), it's a monoplane, and it's got two engines, and it is a Mosquito!
It's the Mosquito NFII of Tony Agar, who started the restoration in the early 1970s, with some small sections and a cockpit, and it now has both engines running, and is based at the Yorkshire Air Museum, Elvington.