There's a "fix" detailed on a few sites now (Windows 8.1 Preview build finicky for UK users to install, but here's a possible workaround - Pocket-lint is one). Didn't work for me (UK-spec Surface RT with Australia settings).
The update is mentioned as only being available for EN-US, but the error message could be a lot friendlier.
Not doing MS's rep much good. And kind of reinforces opinions about Americans being a bit insular :tongue: