I'm not sure I believe [the rather interesting theory][1] that it's a sanitised version of *"Christ on a cross"* (cf the overtly blasphemous ["Jesus Christ on a bike!"][2]), but I've always been partial to...

> [*"**Stone the crows!**"*][3]

Apparently the general consensus is it's primarily/originally an Australian term, but I quite liked a [Scottish rock band of that name][4] in my early teens, so it's always seemed perfectly "British" to me.

The more common (and more definitely, *British*) [*"**Stone me!**"*][5] doesn't strike me as blaspemous.


  [1]: http://english.stackexchange.com/a/79064/2637
  [2]: https://www.google.com/search?q=%22Christ%20on%20a%20cross%22&btnG=Search%20Books&tbm=bks&tbo=1#q=%22Christ%20on%20a%20bike%22&tbm=bks
  [3]: https://www.google.com/search?q=%22Christ%20on%20a%20cross%22&btnG=Search%20Books&tbm=bks&tbo=1#q=%22stone%20the%20crows%22&tbm=bks
  [4]: http://en.wikipedia.org/wiki/Stone_the_Crows
  [5]: http://www.oxforddictionaries.com/definition/english/stone