Interesting news on the free radicals.
Unfortunately we only have a marriage listing for Mary Reynolds and Edward Burbidge - no licence and no register entry, so also no witnesses or other family information. (We could really do with these.) We only know that they were both from St George, Southwark, him a widower and her a spinster. Oddly, although they lived south of the Thames, they were married in Holborn, to the north of the City of London.
I have been looking for info on Mary Reynolds' birth and on the witnesses. One speculative possibility is that John and Ann Reynolds were Mary's parents. If so, she might have been christened by parents John and Ann on 23 March 1726 in Horsham, Sussex (where the Harffys came from). Probably the same parents also christened children Ann (1724), Henrietta Maria (1729), Elizabeth (1732) and Bethia (1735). I haven't yet found the parents' marriage, death or a will, or indeed anything useful to show whether this might have been the family.
Another John and Ann Reynolds had children Sarah, James and Isaac, in St Thomas's (parish next to St George the Martyr) in the 1720s. This might have made them our Mary's uncle and aunt, but still only very speculative.
Back to Marlow/Marlham/Marcham. My doubts are: 1) that as far as I know the Phipps family lived in the City of London. Mary was Christened there and her father was buried there a few years before her marriage. I think I can see tax records showing the family living there through much of that period, and probably for Mary's mother after her father's death, although I can't be sure of this. Mary's brother Jonathan Wathen Waller certainly served his apprenticeship in the City after his father's death. I have never heard mention of any connection between the family and Vauxhall, 2) that the signatures of Mary Phipps on the first marriage and Mary Marcham/Marlham look completely different, 3) that I don't recognise any of the witnesses at the early marriage, 4) that the name Marlow seems to be confirmed from various sources and is also clearly written by the clerk and in his signature on the marriage register, but the name on on the marriage to Thomas Blunt could be Marcham or Marlham, but really couldn't be Marlow (it's also clearly written twice), 4 that although the various places mentioned for the Marlow/Marcham marriage, births and deaths are all close to each other, they are all in different parishes; people tended to use their parish church, so this would imply several moves in a short space of time, 5 that there were many other Mary Phipps around at the time who might have married George Marlow.
In short, too many discrepancies and not enough confirmation for my likes.
Sorry to be negative about this.
Alan