In a phrase like 'each has a different style and attitude' which is the head noun?
Is it right that the head noun can only ever be one word, so I couldn't say it was 'style and attitude'?
Neither noun is the head. "A different [style and attitude]" contains the bracketed coordination of two nouns. Each element in a coordination is of equal status and hence coordination is said to be a non-headed construction.
It contrasts with the non-coordinated "Each has a [different style]", where the noun "style" is head of the bracketed nominal and the modifier "different" is a dependent of the head.