The question is where were they radacalised?
From birth? From a religious building?
I think the assumptions will likely be correct.
Major update from counter terror police about RAF Fairford arrests - all UK nationals:
Male, 24, Resident of Borough of Camden
Male, 24, Borough of Westminster
Male, 25, Borough of Westminster
Male, 23, Borough of Westminster
Male, 24, Borough of Willesden