A wee update. Work on the car stalled out as the DVLA refused me a registration on two counts: the MOT tester had put the car down as a Honda Civic, and the DVLA claimed I had not provided enough evidence of the car's date of manufacture.
The car was back in the MOT place yesterday, and it passed again, this time as a Honda Prelude. The big issue was that the alternator on the F22 is goosed, so it ran out of electricity in the MOT testers bay. I had to take the battery out of my 5th gen and race up there to swap it over, after that it was fine.
I originally supplied the DVLA with the proof of purchase from BeForward and the export certificate, both of which show all the car's details, but this wasn't enough for the DVLA guy. They sated that the DVLA wants the first registration certificate, and of course this is not supplied with the car. All exports are deregistered before leading Japan. I found two Japanese companies that provide exported car information:
https://carvx.jp and
https://japancarhistorycheck.com/
For £20 carvx gave me a document that details all the basic car information, but also the car's auction history, showing all the previous auction sheets and photos. I can see what the car has looked like over the past few years as it has gone from auction house to auction house.
I have just paid £100 for japancarhistorycheck to provide a copy of the original registration certificate. I should have that by email sometime next week. This will allow me to finally get a registration. I have never had this issue with registering previous imports, maybe they have tightened up, or I unluckily got someone very pernickety.