You can have Agincourt though there were three units of Welsh Archers in Henry's army, Arnhem we collectivley lost with the Poles and Market Graden as a wholewith the Yanks, Canucks, and the Free French, Mons a collection of "pals battalions" from all over the UK making up infantry regiments, Hastings a collection of Saxons and Vikings fighting the people who MADE England, the Normans.
The Union FLAG (only a jack when flown at sea) is the collective flag of England, Scotland, Wales and Northern Ireland.
If nothing else you poem shows that we "the British" are simply a collective of anglicised b@st@rds from various tribes. None of us have a real identity because it's been hammered out of us all over the centuries to be Britain.