Hi Phil,
I find your problem a little curious. I am assuming that the disc you have currently in your XJ R is a Denso, which I believe is 25% owned by Toyota. Denso is a huge international company with a Coventry address :-
Denso Automotive.
Eden Road, Coventry. CV2 2TB, Tel No: 02476 843410.
It might be worth a 'phone call,
There is also Denso Manufacturing Ltd, Queensway, Telford, TF1 7FS, 01952 608 500
Regards,
Peter