Like you said it depends on geographical area, type of service, position etc. I imagine private work pays more than NHS work, but you get pay increments for every year worked in the NHS so it can increase pretty substantially.
The other thing is that CPs working in the NHS will often take on additional/different roles which incorporate a management, strategic or director-type capacity which usually provides a salary increase.
Then you have research psychologists who again may work for universities, NHS or private companies and this varies as well.
You can also have income through publications (normally books) or training development/provision and teaching which varies again.