@Incandescent:
You are spot on .
XJ62404158
N44GEB
So, did you tell your relatives about the ULEZ and the need to pay the daily fee for the car ?
Chigwell lies just outside the ULEZ area, near Loughton in Essex. A Driver wanting to get to Dover, would therefore have to use the M25 and Dartford Crossing, or use ordinary roads outside the M25. Have you had a PCN from Dartford Crossing as well ?
All I can suggest is that you submit representations based on what you have told us. The other thing to check is the emissions values for the car, as TfL have not been correct in a few cases.