Let's write this the logical way eh ?
You were on 3.2 and for some reason known only to yourself........ you changed the shop to USA.
Then your little bro updated to 3.4..... locking in the shop channel as USA
You then downgraded again to 3.2 but the shop channel will not alter from the locked in setting......
I did some digging around on your behalf, and here's what I found from a guy called Radio Shadow
1 - Format the Wii Shop Channel account (have to go into the Wii Shop Channel Online to do this).
Note: At this point, do not go back into the Wii Shop Channel, otherwise it will just create a new US Channel accont.
2 - Using Homebrew, open Any Region Changer (google it).
3 - Change the Country to the UK
4 - Save changes and exit to the Wii Menu.
5 - Now go back into the Wii Shop Channel. Just follow the instructions and it will create a UK Wii Shop Channel accont.