So having a bit more of a tinker today.
Seat sorted except for the broken seat lock...I got a replacement one which turned out to be equally useless as it's from a 500T and you guessed it, different from the 450 yet again :-(
Ran into an problem with stator cover though...drilling out for the screws in that cover I had cast, which is going well, but when fitting it up, the screws aren't finding anything to thread into??? Doesn't feel like any threads in the rotor?
Pull apart again tomorrow and investigate by the looks.
Not sure yet whether to cut the rear guard off, or just find a neat taillight to suit??