HPI check on personal plate

[.Adam.]

Hoping to go and look at a car to buy tomorrow, which has been on a personal plate. I assume that he has just taken it off the car as it doesn't come with this plate, so when I do a HPI check, do I do it on the private plate that has just come off, or the new age related plate, or doesn't it matter?
Also, he states that a HPI on the private plate will show up a couple of CAT C/D markers on different cars, I assume this is okay, just as long as it doesn't mention the current car?