Anton, you've recieved a heap of good advice esp getting yourself the book The Tree Climbers Companion by Jeff Jepson
also getting onto ???????? forum, you should also try
http://tree-tech.com/eve/ubb.x?cdra=Y&s=508606541 the knothole forums you have some of the best UK tree climbers on that one.
Hoping you are legit and not a troll. If your base is Warickshire then David Lonsdale is just up the road from you get along to one of his seminars.
Ultimately there is no short cut to experience, dragging brush for months under some of the best climbers I've seen taught me more than any book or email. Climbing comps are fun to watch and the guys are all (IME) super helpful and willing to spends ages explaining how and why and why not.
SF