I agree. The Z number checks out.The reg number, if I am right is the post war number allocated to vehicles. The disposal numbers are always a mystery to me, if only there was a list, you might find out the area it was disposed in, the TWN may suggest its are, like Twickenham for example. From what I remember there were 3 contratcs for the C8's all 1944 dated, but will have to dig out that info tomorrow, I think it was originally in Wheels and Tracks. Has it got a rebuild number on the chassis plate? You should find that ties in with the number on the record card, deciphering a bit of the mystery.
And for what its worth, it cant have been in any worse condition than mine when I started!