Matthew
do you mean the aluminium one that is riveted on (or do you mean the actual piece of metal that the number is stamped into in the front trunk on RHS - UK driver side) - I hope you don't mean the latter :eek:
if it is the aluminium one there should be two tags on the front latch panel - one the vin tag and the other the BS AU 48 tag which I think is about seatbelts or similar - all UK cars had the latter plate
Here are some photos of them on a UK delivered 69S
Attachment 503708Attachment 503707
your car, as it now sits, probably does not have that panel to fix it to at present