Another photo found in the attic clear out is this one. My old copy of the Register would suggest that it is PB 0484 but when I check that chassis number it is shown as JZ 6858.
1982 Register lists it as JI 6858 belonging to a P.J.Wells. It was listed the same in the 1986 Register
In the 1986 Register JI 6858 cross references to PB0484 as I said in my original post. But if one checks the entry for PB0484 it is shown to have the registration number JZ 6858. And JZ 6858 also cross references to PB0484.
Clearly a bit of confusion somewhere along the line.
It would seem that the Register might be mistaken in referring to PB0484 as JZ 6858 as the JZ series ran from October 1946 to August 1954 whereas the JI series ran from December 1903 to February 1944. So the JI number would be of the appropriate period for a PB whereas a JZ number would imply re-registration in Northern Ireland in the 1950s. Not impossible, of course, but perhaps more likely that it's a simple error in the Register listing?