Windows has an officially supported international keyboard layout for the US with AltGr-initiated dead keys for composing characters. Unfortunately there is no equivalent for the UK; the UK international keyboard layout is completely unusable for programmers as it turns a lot of commonly-used keys into dead keys.
But there is a decent international layout for the UK available from here:
http://www.chiark.greenend.org.uk/~johns/kbukint.html
