1841: Bridget McCann aged 45 Preston, Lancs
1851 Bridget MacCana aged 55 born Ireland living market Weighton
1861: Bridget Hartley 65, William Hartley 60, Martha Hartley 13 (born Thirsk) - this Bridget Hartley is in fact Bridget McCann,macanna,maccana. She is too old to have a daughter of 13 so likely this Martha was a grandaughter. She is born in Thirsk in the correct year for your Martha and has a grandmother called McCann. Could there be a link?