UK National Health Service
There isn't one.
There's one in Scotland, and one in England, and although they were (originally) both set up in the same year, i.e. 1948, they're wholly different and quite separate organisations.
I'll bet that many people out there not only know that Scotland has it's own quite separate civil and criminal justice legal systems, but also that the drink/drive limit in Scotland is just over half of that in England and Wales. "Even" the BBC weren't aware of that when they produced an hour-long programme with multiple references to the "UK drink/drive limit" throughout... :-(