When people ask me where I am from, what should I say?
I would say, I'm from Western-Super-Mare but currently living in Wales.
I can see your problem. Most people from Aberdare, and just about everybody who is from Newport would like to keep quiet about the fact. Say 'South Wales' and hope they don't ask any further.
Say you were born in England but you've moved around a lot.
"All over".
The UK