Hi all, the comments about the first UK CB750 are correct, it is chassis number 1010369 and it's sitting in my garage as I write, having had an outing to the pub last night. Always a hoot to ride and far more involving than my K2, really surprisingly different. This first UK production bike was manufactured on 22nd October 1969 and sent as part of the first UK batch (not sure how many, 12 has been suggested) to Ken Ives motorcycles of Leicester, where it was sold and registered in January 1970.
There were no UK spec sandcast bikes, and it follows that any CB750 in the UK with a G registration plate (1969) must be some form of import from a country that received them before the UK, which appears to be quite a lot of countries.
Mick............kettle738