Stereotypical, recognisable, educated version of "gosh"

Is there an expression like "gosh" that a stereotypical upper-class British character would say for expressing surprise?

I've thought of "parbleu", but it being a loan word from French, it doesn't sound right as a stereotypical English expression.

I would avoid "My Lord" because of possible moral implications with the reader.

Note: it should be easily recognisable by a non-English audience.

Is there such an expression? Thanks!

I think “I say” is the term for you. This is my reasoning: Oxford considers “I say” to be both a British form of exclamation as well as a “dated” one (I prefer to call it quaint). The upper-classes were very likely to use wonderfully old-fashioned language in keeping with tradition. Thus, the older the word, the more likely the upper-classes used it.