Thank you to everyone who has been helping with my query. I'm overwhelmed by your help - and so very grateful. I've been looking for some detail on Daniel's life in NSW but can't find much as yet. BDA says he returned to Britain on the Kelso, leaving Sydney on 20 March 1841, and he died in Wirksworth in August 1844 (thank you for the newspaper article, hanes teulu, and the information on his military pension and death, Tony).
I'm assuming he and Mary met when the 17th Regiment was in Galway between April 1827 and May 1829 but am yet to find any evidence that they met again after Mary was arrived in Sydney in 1834. Daniel could have been anywhere of the many places the 17th Regiment was sent to in his time in NSW.
Suzan