So I found the following question, and the top answer here seems to confirm that there is no location specific damage in Skyrim (so no benefit to headshots for instance):
Unfortunately the answers in that question did not address how armour affects the damage calculation. The top answer that did some location-specific damage testing, but did not appear to do any armour-based testing.
My follow-on question is whether armour protection is location specific or cumulative. For example, say I have armour on my chest, feet and hands at 50 points each, but I'm wearing no helmet - does my head benefit from 150 armour, or zero armour?
To put it another way: If I wanted to play a character who doesn't wear a helmet, does that put me at a major disadvantage (because any headshots would effectively be against an unarmoured target) or a minor disadvantage (because my cumulative armour total is slightly less)?