Scorpion,
Sorry, I wasn't clear enough.
Firstly, the SC9 designation is not a mark number. SC isn't a role designator like B-for-bomber or
PR-for-Photo Reconnaissance. It was the SC9 in just the same way that the Belfast C.Mk 1 was the SC5. Nor was the aircraft ever in 'proper UK service' (by which I meant RAF/RN and not MoD(PE) or RAE/RRE).
Secondly, there was no MAR for a B.Mk 2/6 meaning that the designation is unofficial, in just the way that the B6RC and PR16 designations sometimes applied to 51's Canberras (and seen on some of the relevant record cards) were unofficial, and in just the way that the RAE/RRE B6/8 hybrids probably laboured under a host of unofficial and semi-official designations. And again, WK163 was never in 'proper UK service'.
Beeayeeight,
It was from memory, because my Canberra books are in my archive/store at the mo, which is why I couldn't recall or look up how many seats the PR3 had, nor the B(I)6, nor the PR7, nor the B6BS, nor the B16.
It might also explain how I missed an RAF Canberra variant designation! (Wonder if anyone will spot it?)
I thought that the B(I)8 was derived from the B6 (big Avons, integral tanks, etc), but with the new nose and gunpack. I hadn't meant to suggest that it was derived from the B(I)6.