To work in CAMHS you'll need undergrad and postgrad degrees in psychology - the undergrad one can be a straight psych or combined with something (I'm doing mine with counselling skills).
Check the courses you might choose to see if they are recognised by the British Psychological Society - this ensures that you'll be taught the basic requirements to specialise in any area once you've finished the undergrad. degree. You'll need to pass with a 2:1 or higher to get Graduate Basis Requirement, which will allow you to go on to specialise in an area that interests you
and get Chartered status. There's more information
here.