My ethnicity results don't really tally up either, combined total is 55%, the split is 38% paternal and 17% maternal. I know DNA has revealed my paternal grandfather is not the man I thought he was (my father's birth cert is not really worth the paper it's written on).
The big surprise though is that most of my paternal matches trees show their ancestors in Lincs and Leics whereas my maternal relatives seem to be in Ireland. My maternal side has a paper trail back to the mid 1700's and every birth, marriage and death is within a 10 mile radius of Lincoln, there's nothing at all that has any connection or even a suggestion of an Irish link. My DNA results are effectively the complete opposite of the paper trail.