Yes, I know it is not possible - at least Microsoft moderators will try to claim it but it is a lie.
What's the problem? I have my Xbox Live account associated with my Microsoft account for almost six years. I bought my Xbox almost four years before Xbox Live was officially introduced in my country. As many others I used address from supported country to register to Xbox Live and use my legal Xbox with legal games. The address wasn't made-up. I indeed lived there for a while.
My Microsoft account (formerly Windows Live ID and .NET Passport before that) exists for a long time - much longer then my Xbox live account. I have many services associated with the account and I'm not going to change it. My most recent service is quite important for Microsoft - it is Windows 8 from MSDN.
The problem is that Windows 8 use both Microsoft account and Xbox Live ID for some services. If Xbox Live ID's region do not match region of your computer it simply doesn't work:
Your Xbox profice doesn't match your Windows region. Go to control panel, Clock, language and region, change location, select United Kingdom, then restart the application.
What a wonderful help! Except simple detail - I'm not going to change my computer location. I want to change region of my Xbox Live account! That goes back to the claim that it is not possible. Well it is - after Xbox Live was introduced in my country it was possible to migrate account to different region directly on xbox.com web page. I don't understand why this option is not available permanently especially where it has impact on user experience with Windows 8 and Windows Phone devices!