Here is my answer, generally there are several
IF you know the original numbers, then YES you can order and insert new tags and YES you can go from single tag to EID double tag sets.
Defra are never going to mind extra ID it is the too little ID they have a problem with.
IF you DON'T know the original numbers then you replace with RED tags and can again double tag but this wouldn't apply to your case as you know the numbers