Well, an almost instantaneous response from John.
Main changes are to the cabinet, with Mk 2 have better bracing internally (difficult/not really possible to upgrade); newer bass unit (possible with some woodwork), new tweeter (larger holes in mesh, in case anyone's trying to ID a pair, but the same size I think).
Yes, John is a real enthusiast, and very helpful!
Can't work out how to post images but if someone guides me I will add them or I can email if interested.