HPI are OK, nearly got a WRX from a trader in Somerset that had outstanding finance on it so yes do it and they will also tell you on the phone if there is a problem. They put me in touch with the finance people who confirmed that the car was not paid for. The more info you can give them the better, Reg. number, mot cert. number, chassis number and so on. And if they get it wrong then you can reclaim up £10,000 if I remember correctly.