The Pokemon Bank will charge you £4.49/year to store your Pokemon there
Nintendo has just published the Pokemon Bank prices for Europe, and they're in line with the already-published $4.99 US cost.
A one-year Pokemon Bank subscription will set you back £4.49, although you'll get 30 days free after you've downloaded the app from the eShop.
As well as being able to store up to 3,000 critters in the Pokemon Bank 'cloud', you will be able to transfer monsters from Pokemon Black and White and Pokemon Black and White 2 into your Pokemon X and Y games using the Poke Transporter companion app.
So, if you're serious about building the best Poke teams and winning all the Poke fights you can, then you really should download the Pokemon Bank app on December 27th.