Thank you. Yes, finding anything on William is proving difficult!
His occupation on the birth certificate is 'general labourer' so doesn't give much more to go on but we do also have an address which is Ann Street, Lancaster. There was a mill close to Ann Street, some of the records from there are in archive in Preston, but they don't have any record of William Courtney in them, unfortunately.
Could you recommend a good site for searching electoral rolls?