We are all probably aware that the UK is composed of four constituent nations - England,Scotland,Wales and Northern Ireland. A number of protectorates also comprise the greater UK which can be easily researched on Wikipedia. I’ll provide a link later. However throughout the history of the British Isles there have been numerous independent polities post Roman era most notably during the “dark ages” and the early medieval period.
In your opinion what other “constituent” or independent nations may have existed for longer or may still exist with a POD after 500 c.e? Also please consider or postulate nations that never existed in OTL but may exist in an ATL....