Thanks Kghost.
The rack was fitted by the original owner and I think is an aftermarket one. It apparently also had a screen on it which was taken off by another previous owner (thankfully as I don't think I would have liked that). Hence the indicator stalks are in the wrong place.
Unfortunately any smaller and the numberplate would probably be illegal (though plenty of bikers do make them smaller particularly race bikers). I could probably cut some of the black outside down but the numbers have to be a certain size (for the ANPR systems that are around to catch speeders and road tax dodgers etc).
The thing that most reduces top speed is having my fat arse on it