You cannot pay ArenaNet directly. You need to preorder the game to play in the betas (although the 18th February is the last one) and to buy the game to play it once it's out.
Maybe you could attempt to purchase it in UK once it's out?
Now I understand. If you say that February 18 is last beta weekend, then sure there is no reason to look for preorder package. I will seek for release and probably you right I will look in UK, as my favourite game store in Helsinki doesn't have it.
"Endure. In enduring, grow strong."
-Githzerai adage.
