The funny thing is British was the name used by the Romans for the Cymri (Welsh), which is why Cymraeg (Welsh) is known as Brythonic gaelic.
The English are not primarily Celtic. They are the Germanic Anglo-Saxon, and should properly be called English (Angle).
This council is ignorant of their own history.
Go check your history and linguistic knowledge. The Romans referred to "waleas" or "foreigners" from which the name "Wales" is derived. The Welsh refer to themselves as "cymru" or "friends". The Welsh language is Cymraeg which is a celtic language of the Brythonic branch (along with Cornish and Breton). The Goidelic branch includes Gaelic (Irish), Scots (Scots Gaelic) and Manx.
The Welsh and Scots have existed under oppression from the English for centuries. I can well understand why they reject the broad brush label of "British". They are culturally, linguistically and ethnically different from the English.
Hwyl!
All to the good to get the information about the make-up of the once United Kingdom. I know you are probably well versed in this, but for others it may be of interest in the now passe histories. I daresay what my old school teacher in England during the war years is now heresy. We know that when the Roman Legions left around 410 ad to defend Rome, the indigenous people slowly began to come into their own.
Then the Germanic peoples came from the great river, the Angles, Saxons and Jutes. They poured into the land, not their own. Savage warfare errupted with the Welsh. The Welsh stood them off successfully. The Germanic peoples mainly held sway where England is today. Then came the Norman French in 1066. The conquest.
Alas, neither Welsh, nor Scots, nor Irish and English today, are such as some of them claim. They whistle past the graveyards. The juggernaut of multi-culture. I will say no more. It gives me much grief.
Even funnier: "Welsh" was the Anglo-Saxon word for "foreigner"
Caerphilly council: "Ich bein ein foreigner"