"either Jersey or Guernsey"
Both are not EU members - I don't know what will happen to their treaties with EU when UK exits. Because they are usually regarded has "tax havens", there's some risks involved in stashing money there, as some loopholes could be closed.
I really hope once UK is out, Channels Islands are also kicked out fully - although all we know politicians and their friends like a tax haven at hand.
Anyway, while they could be good as a "fiscal residence", they are not exactly the best place for an European HQ and the people working in it, I don't think Apple has any incentive to move it.
Apple started to move to Jersey well before the Vestager investigation. It started when EU began to close loopholes like the "Double Irish".
Biting the hand that feeds IT
