I did a lil digging into this after read either Fastford or Performance ford, about Di's car.
There was 3 reg as black, but only one painted frome bare metal to black and that was the one Di had, and I believe that she didnt buy it but it was on a long term loan form ford, once ford got it back it they changed the reg and removed special radios and other extras. The other black ones were done to special order and repainted the reg as black.
Di's black one is prob the most expencive rs turbo ever, once read that a collector from the US bought anther car owned by Di and paid over $250,000 for it.