First off, Im glad you have found a thread that helps you. Bill is a great guy and continues to be a massive help for many people here.
Now the naggy part.
I sense a bit of a cop-out Phil. You are only..21 is it and you are saying that you had therapy a few years back? That would have made you a teenager with rampaging hormones and things have probably changed since then.
You seem to be looking for reasons (maybe subconsciously) to avoid taking any kind of long term action against your anxiety by more or less saying you are not feeling desperate enough..that doesn't make sense my friend.
You also state with certainty that therapy would be a quick fix and the anxiety will return-how do you know if you don't at least try?
Yes there are waiting lists but Phil mate..again, that doesn't really make sense.
What you are doing now, is it dealing with your anxiety? Surely the quickest fix of all with guaranteed rebound effect is to post here for reassurance, get it and then post again soon after?
You have looked at CBT books and relaxation-do you put them into practice regularly or have the books been relegated to the bookshelf?
I can't make you do anything you don't wish to, nor would I want to. But what i would say is if you are really serious about wanting to feel better, you will take a long look at what you have done so far and ask yourself if you have really given it a chance to work or have given up as it's seems too difficult.