While we are all part of the UK, it is all in together or all out together.
Each county's vote might be to stay in or to leave, each town might come to its own conclusion, each individual might vote differently from the rest of their county, their town, their street. however, it is the UK as a whole which will reach a decision, not each separate part of it.
If one region doesn't want to be part of the whole, then they need to separate themselves and negotiate their own in/out. Four separate deals for England, Wales, Scotland, Northern Ireland. But wait! The North of England might not want the same deal as the South! The Home counties might want to negotiate separately from the West Country! We could have ten or twenty different deals.
The important word here is The United Kingdom.