https://en.wikipedia.org/wiki/Charles_V,_Holy_Roman_Emperor
Our last ruler of that name was Charles IV, we're still one Charles short:
https://en.wikipedia.org/wiki/Charles_IV_of_Spain_and_His_Fa...
https://dbe.rah.es/biografias/10728/carlos-i-de-espana-y-v-d...
Edit: it's just wrong is what people object to. She was the first Elizabeth of the country. Same thing for James VI (not James I which was a different dude).
Seemingly the government agreed because mailboxes in Scotland don't have EIIR : https://en.wikipedia.org/wiki/Pillar_Box_War
https://en.m.wikipedia.org/wiki/James_VI_and_I
Likewise for his son, James VII and II.
AFAIK Elizabeth is the only post-Union monarch who took an "England only" regnal number that didn't gel with Scottish history.
I guess we're in for another round of this when Charles dies and William the "fifth" takes the throne, although at the rate we're going Scotland might be a republic by then.