Sadly, I've had the same experience; common Irish surnames, frequent first names, variable ages given in different English censuses, and - as you say, simply "Ireland" as a birthplace. One even seems unable to make up his mind if he was born in Ireland or Wales! I think such a lot was down to the enumerator, and, especially with young men working away from home. information would often be spoken by a fairly illiterate householder, to the enumerator, and neither party either knew nor particulary cared where lodgers originated. They certainly were not thinking of us all wanting to know where our roots were before they emerged from the Irish sea, were they?