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Blizzard are advertising the new battle chest digital download for only £4 (Eur 5 or $5 US) which includes WoW with the Burning Crusade and Lich King expansions now as well as your first months sub, so if you have never played before you can have a look and get a feel for whether you like the game or not without an huge outlay.
I believe that the Panda's start area will also be available to you no matter what level of expansion you have, although you won't have access to Pandaria as a whole without upgrading to that (which of course requires Cataclysm as well).
£4 for a little nostalgia, a dip in the waters if you haven't tried it before or just a month of annoying trade chatter, what are you waiting for?
It must be Thursday, i never could get the hang of Thursdays.