Joining a centre

Why, in this modern digital age, can I not join a centre online? I was going to join my local Centre (Norfolk) but need to send off a slip from my membership pack, that I do not have, as I always renew each year. Secondly, why do you have to re-join a Centre each year? Thirdly, why can I not join more than one Centre? After all, it seems that some have more things to choose from!