With WoD on the rise Blizzard thought it was time to up the anti on the prices in Europe. On the 13th of November the prices will change as follows...
(the old is in parenthesis)
30 Days - £9.99 (£8.99)
90 Days - £28.17 (£25.17)
180 Days - £52.14 (£46.14)
The 60 day prepaid will be bumped up to £20.99
Those who are currently in a recurring sub plan (up until the day of the price change) will see no change in payment for two years after the price increase, just as long as you don't alter your plan. So, if you plan on sticking it out for the long haul, I suggest you lock in your recurring before November the 13th.
Source: Secure your current recurring subscription price for two years - Forums - World of Warcraft