Philip, you need to buy your parent's birth cert which will give details about Richard Corrin and your grandmother, including her maiden name. From the information given there you could then buy their marriage cert. which will give their fathers' names and occupations. That should take you back early enough for people to be able to help, if you post the full details on the board.

If you live in Australia or New Zealand their death certs would also give a lot of information.

Sue