Carl, I think most university courses require A levels or equivalent, so I would agree with the person who suggested a agricultural, horticultural or arboricultural course.
There is a college near me (in Durham) that runs full and part time courses on Environmaental conservation, which might suit you to a T.
East Durham College East Durham College East Durham College
Have a look at some of the courses, then look at colleges near you to see if they offer anything similar.
Also:
East Durham College