With the dawn of the internet proper it is not really necessary to join associations these days if your only looking to aquire fish (you just gotta know where to look and how to look) and numbers have dwindled steadily because of this, but they do provide that personal touch, meet new friends and generally aquire things that you'd only ever seen in books. I would say the BKA and the AKA do not suffer fools gladly and you will have to be dedicated to be accepted properly. Back in the early eighties it was a boom time for local associations etc, but sadly things have declined and there arn't half the clubs around today.
So joining a local club or international body I would say is entirely up to the individual, who must ask themselves what can I get out of this. My answer is "you'll only get out of something what you are prepared to put in so with that in mind the decision is yours.
Regards
BigC