You can modify your Wii at home, all you need is an SD card to perform the BannerBomb and install the Homebrew Channel... Or Zelda: Twilight Princess to run the Twilight Hack and install the Homebrew Channel.
I hope this information was useful.
Though if you are looking to get your console fitted with a mod-chip, there are many places in West Yorkshire, mainly Leeds. Although I don't know the area, but there are many websites from and around the Yorkshire area who sell and fit modchips.
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