Hello!
This is my first guide ever posted on ownedcore, so excited!, I've discovered it all by myself and I wish to share it with you guys!
1. Get Firefox.
2. Install addon called Tamper Data
3. Login in into your account on battle net page, go to the page where you change your address (and where you used to change the country).
4. Press ALT, look at top, click on Tools and then Tamper Data.
5. When new window opens, click on Tamper Data in left top corner.
6. Go back to battle net page, click on Save Address button.
7. Message box should appear, click on Tamper.
8. New window should open and in right bottom corner you get "hasCountryChanged" and "newCountry". Change the value of "hasCountryChanged" to 1 and "newCountry" to GBR (to get Great Britain, use other values for different countries, like FRA for France).
9. Click Ok.
10. You are done (dont forget to click on Stop Tamper when finished)