GaryJ always used to advise with the Sammios that you could get it registered and inspected as soon as the body was bonded on.
Here was my old Sammio inspection at VOSA Poole:
So you can see what stage the car was at then. Frame on, Body bonded to frame, no Bonnet.
He simply double checked that the chassis hadn't been modified and checked the numbers on engine, chassis etc.
I know things have changed a bit now so we no longer have that inspection, but i can find no reason in all of the updated paperwork why you can't register it at the same stage as i did the Sammio?