Sorry, can't help with the import registration. Just like to point out it might take a while to get sorted. Sent my V5 for a 1980 CD200 to Swansea for a change of taxation class to Historic Vehicle, fairly basic and straightforward. That was in mid May and it arrived last Thursday, so, about 14-15 week turnaround. Apart from Covid issues, Swansea are having industrial action problems. In all my dealings with them, I photocopy everything and get proof of postage. Good luck with it all.
Ron.