I find it interesting that you're willing to say "twat" but not "bastard". I admit that I didn't think of either of those words, though I think they're still much tamer than the ones with "u" in them. Really what I was thinking of was "crap" and "damn".
Regardless of variance, I don't think I'd regard either the above or the name of a fat character in Austin Powers as "tamest of the lot".