You guys are amazing!
Pretty sure Thomas (b 1840) came to Australia on the Wansfell in 1863, and met his wife Ann Reid on the same boat, although she's not listed until the 1865 trip, but they were definitely married 28 May 1864 - there's some crossing out and confusion on the top of the page of the register, so I think the 2 trips passenger lists may have been a bit mixed up? He went on to be a successful building contractor and elected to Brisbane City Council, but died just a few months later aged 38 in 1878. It's his son Thomas Mortimer Walters who's on the electoral role.
Just found that George Mcmaster married Jane Simpson in 1821 in West Derby, fits with the witnesses for Horatio's marriage. (Love finding out more than just the names, so interested in the stories! Thanks for the info about Horatio.)
Still wondering what's happened to Jane Walters nee Mcmaster? I have a suspicion she may have come to Australia too, there is a reference in newspaper to Thomas' "distressed wife and mother" when he seems to go awol for a bit in 1867, but it's a bit ambiguous.
Would most like to know where Thomas Walters snr and Jane Mcmaster were born so that I can continue the search.
Thanks for all your help!