Perhaps you need to look at Plaster/Barnfield marriages? There is a Jane Plaster, 16, with possible mother Elizabeth in 1841, and also a Henry Plaster/Plaister whose parents on the IGI are William and Elizabeth. I think Jane is on the IGI indexed as 'Haister'. William Plaster m. Elizabeth Bunting.
... on
www.a2a.org.uk, there is a mention of a Richard "Bunting alias Barnfield", in Tetbury. (This isn't making things less complex, is it?)
I was wondering why I couldn't find this family on 1861/71/81, and then I saw this:
http://www.immigrantships.net/v5/1800v5/chance18600713.html - Jane/Emma Jane doesn't go with them? They left in April and she married in December quarter. I see she also has a daughter Emily A. Mann with her in 1861 (it seems they came to NSW later).
Births of six more children to Meilburn are listed in the NSW birth index, as well as children of Emma Jane (m. John Harris). Also, several deaths and marriages for the family. The spelling of Milburn/Melbourne/etc's name changes a lot.
So, the question really seems to be: was the Jane who was the mother of Emma - Jane Plaster who later married her father (16 in 1841) - or was she Jane Barnfield (aged 13 in 1841) and Emma's father happened to marry another Jane.
I am not sure that Jane aged 13 in 1841 is actually the daughter of William and Weltham, incidentally - they seem too old, and IGI shows they had another daughter Jane, ten years older, who married in 1838. She might be their granddaughter or some other relative. This Jane doesn't appear to have married in Tetbury - so what happened to her?
