This is English-style cheddar which, while undoubtedly the original and most authentic, is very different from American-style cheddar; it has a sour taste to it that most of us don't really care for.
California mild cheddar is something I have never seen here.
There is always the fake stuff, the "pasteurized process cheese food" with cheddar flavor. Sort of. It's not as bad as it sounds.