My tree matches the Preston Baggot line you described pretty closely. Mary Avern b. 1862 married Thomas Leighton b. 1852, who was my G G grandfather.
I can also match up the others you mentioned, altough some of my dates are slightly out.
I have a Thomas Avern b: 1825 living at Oldfield Farm who married Harriet. I think this is your Thomas Avern 1823.
I haven't got any further back than John Avern b. 1778 though.