Hello
So the structure of the NHS is actually four separate governing bodies that are independent of the government: NHS England, Scotland and Wales, and Health and Social Care in NI (Not NHS Ireland). These are allocated block funding by Westminster through the Department for Health (which I think is dependent on the population demands on healthcare under each body), but aside from that, these are quite independent and are able to make decisions about the NHS in their own countries.
Within these different governing bodies are different local bodies that manage health care in their local areas, called Clinical Commissioning Groups. These are made up of GPs, nurses and consultants, and they are in charge of commissioning health care in local areas (so they make all the decisions as to how local care is managed). NHS trusts are a system of interconnected hospitals, GP practices, mental health services and social care services that carry out the commissioned service from the CCGs.
However, recently there have been talks of more devolution, that is to say that even more power should be transferred from Westminster and the Department for Health to CCGs and similar local groups. The hopes of this are that services would be even more aligned to what each region in the country needs.
Hope this helps and let me know if you have any questions