The seller might have a copy from the Ford dealer of the import Certificate for Inspection of Completion if it was a new car, which seems it was if imported 2001 and on a 51 plate.

I have got the one for my Evo from MMC in Tokyo, as it was imported new.

If the car has been in the country since 2001, import papers aren't important as the V5 will be suffice. Make sure you get a full HPI check done though.