The Wii U's launch has been successful both in the US and in the UK - I found this article that indicates Nintendo is going to make sure that the UK is well prepared in Q1 of 2013 to meet demands.
Here is a brief excerpt from the article...
It's fair to say the Wii U's launch has been a success, with the system selling out across the United States and shifting 40,000 units in the UK. Extra shipments are coming in thick and fast to meet the extreme demand that you'd expect for a new Nintendo console at Christmas time. Nobody really doubted that Wii U would be successful at launch, but many people are concerned about what's to come.
More can be read here... http://www.nintendolife.com/news/2012/12/nintendo_uk_looking_to_maintain_wii_u_momentum