Yes the Great Orme is a hill or headland on Llandudno. I live a few miles from the welsh border and all I know is Ll is pronounced 'cl' (and I expect that's a simplification).

As for the "nigger in the woodpile" it is a saying, like "the fly in the ointment" meaning a disadvantage or drawback (I'm not sure if they mean quite the same). It was certainly used when I was growing up, not so much now perhaps. Though some people get very heated about the "stupidity" of "political correctness" and will insist that e.g. no-one could possibly object to a harmless children's toy (not my view now)