Find Ancestors

Hi there - come across a few sticking points in my research - fairly new at this and not too sure how to go about the next bits, any suggestions would be really appriciated. (I'm based in London) 1. Margaret Carson (nee Cuthbert) c1817ish? married William Williamson c1820 Ballyclug Church of Ireland 10/05/1846 witnessess - James Mulholland and James McGrath trying to find details about her first marrage to the unknown Carson (and if there were any children from the first marrige) 2.William and Margarets first son - Matthew Williamson c1851 Royal Navy - Jumped ship in Montevideo, Uraguay in the 1880s. Think he ended up in Brazil and may have had a daughter (family gossip) but cannot trace him at all. B,M or D. 3.Williams and Margarets Second son(third child) Married an Elizabeth (lizzie, eliza) Graham - Presbyterian Church Ballymena - 23/09/1880 - Witnesses at wedding - Wiliam John Williamson and Martha Graham. Wedding took place 1 month after the birth of there first son. Trying to trace Eliza's parents and siblings (if any). I have her date of death as 01/12/1944. 4. Susanna Williamson, 01/01/1887. This one I'm more jsut curious about, born in Ballee Connor, N.Ireland, she was a linen weaver, emigrated to Australia and married a Victor Bailey (know nothing about him, irish or aussie? or what happened to him) but she came back for a visit and decided to move back - went to Australia to pack up and her Brother recived a telegram telling him she'd died when hit by a motor vehicle. No idea about what she did in Australia though or if there were any children.