I hope I'm okay reply to this thread a decade later since it's the exact topic I'm curious about.
It's a long shot if anyone knows anything, but I'm trying to find more information on my 3rd-great grandfather William Mills, now that I've finally confirmed he is who I thought he was. He was tried in Wexford around February 1843 for theft from his employer and sentenced to 7 years transportation to Tasmania aboard the "Orator". Before the journey he was imprisoned in Kilmainham and was apparently only 15. He died in Hobart in 1893 and later in life his reported age bounces all over the place, either due to uncertainly, carelessness or attempting to hide his criminal past as some did. His early records around imprisonment and transport were fairly consistent, putting him as being born around late 1827 or so. The convict indent says his native place is Wicklow, and I believe from news articles he was arrested wandering around Newtown Mount Kennedy.
He was Protestant originally but he became Catholic in Tasmania and married twice; his first wife my 3rd-great grandmother was Catherine Dunn who died young, and his second wife was Mary Healey/Haley. The children he had with Catherine were four boys, in order of birth Edward, John, William and Walter. John was Catherine's father's name, so I'm inclined to think William's father's name was probably Edward. Also according to the indent William lists no parents but does list siblings: one brother John and four sisters Mary, Ann, Emma Maria and Betty. Emma and Maria are underlined together, so without commas I'm assuming that's a single name.
So why Rathdrum specifically?
For a start there seemed to be quite a few Mills protestants there, or at least where there's surviving records.
Additionally, William's eldest son Edward (my 2nd-g grandfather) married Charlotte Williams, a Tasmanian-born daughter of Thomas and Mary Williams (nee Williams). Thomas and Mary were also from Wicklow and migrated to Tasmania in 1854. Thomas Williams was the son of a James and Elizabeth (nee Williams) and was from somewhere called Streamstown at Newtown Mount Kennedy, being baptised at Newcastle parish in 1808. Mary Williams was the daughter of a Richard and Catherine (nee

) from around the Stump of the Castle townland near Rathdrum where she was baptised in 1813. I think Mary's family maybe moved to the Glenealy parish which was where a younger brother was baptised and Thomas and Mary were married in 1839, the couple then living at Streamstown at NMK until they migrated. It all seems an awful coincidence that William Mills wouldn't have known this family in Wicklow but knew them while living in separate towns in Tasmania.
As a slight aside, Mary's sister Jane Williams married a James Campbell (occupation "police" or "police pensioner" is all I know about this man) in Glenealy in 1832. Jane and her husband had at least three children baptised in Rathdrum: Samuel, Richard and Catherine. For reasons as yet unknown to me, one of Thomas and Mary's daughters Mary-Jane, born at NMK in 1849, did not travel with her parents to Tasmania. Mary-Jane instead arrived in Tasmania 12 years later in early 1866 with her apparently now widowed Aunt Jane. Another girl of the same age was travelling with them, Kate Reeves, I believe probably the daughter of a baker from Rathdrum named Hercules Reeves. I highly suspect Jane's daughter Catherine Campbell was the Catherine Campbell that married Thomas and Mary's son James Williams, her cousin. The age is right, and Jane stuck to the same town in Tasmania as her nephew James and his wife until she died in 1899.
If anyone has any clues about these particular Mills and Williams Protestants of Wicklow, or even just what Streamstown was at Newtown Mount Kennedy (a farm name?), I'd certainly be grateful to hear it.