Having looked through my files I find that I did have a copy of the page of baptisms for 26 May 1867, which included the baptism of Ellen Catherine Waldron. As I had only been researching direct lines of descent, and not having looked at Mary Ann Waldron's siblings in detail, I had assumed that the John Waldron shown as Ellen Catherine Waldron's father must be John Waldron junior i.e. Mary Ann Waldron's brother. I see now that I am mistaken but cannot help identify a father. The Waldron sisters may have had rather irregular relationships. Mary Ann's and Ralph Milward Smith's first child, a son Ralph, was born out of wedlock. Mary Ann was pregnant with their second child when she and Ralph travelled to Paisley in Scotland for their wedding on 5th March 1861. The only witnesses were a local couple who appear to be connected to the church. I suspect that the quiet wedding was to gain respectability before the 1861 census. Their second son, Arthur Charles, was born on 27 July 1861.
The baptisms in 1867 must have been after the family was perhaps getting back on it's feet financially. Ralph had been declared bankrupt in April 1865 when he was at the Alma Public House, Alma St, New North Road, Islington. By the time the order was discharged in December 1865, he was recorded as having been at the Pickering Arms, Pickering St, Islington.
I have noticed that in 1841 to 1871 census returns there are entries for a William Waldron and his family. William was born in Bath but moved to London. I have wondered if there was any relationship with the John Waldron who married Mary Hummerston. Does he appear anywhere on your tree? - I would be interested in seeing details on the private Stocks Family tree if I may.