Morning John
Mary Ann Clark was Susannah Lawson nee Palmer's niece, the daughter of her sister Sarah Clarke nee Palmer. She was a granddaughter of their mother Elizabeth Palmer nee Vatin. Unlike her auntie who applied for the hospital but was eventually put on the Coqueau charity, Mary Ann was taken into the Hospital itself as an inmate, in July 1897, at the age of 69, and died there in February 1903. She was a sunday school teacher at Dolphin Court Ragged School, Spitalfields, and her brother had been a missionary. Her petition was supported by Septimus Hansard, the famous Christian Socialist and long time rector of St Matthew's Bethnal Green.
I had a look over the old posts Solomon Macaire. I don't think your likely to get any further on him. I've exhausted every avenue open to me with him. I think the strongest theory is he was a child of Jean and Amelie who had a child baptised in West London around the right time 1730's. Perhaps they were new refugees and he was born to them in France shortly before that date? Amelie is actually a quite unusual name amongst London's Huguenots, so it seems fairly good circumstantial evidence that he gave a child this name. The other alternative is he was a new refugee in the 1750's. Either way since neither he or the suspected parents seem to have joined Threadneedle Street their coming over doesn't seem to have left a trace. The tesmoignage registers for these other churches generally don't exist.
The other normal route to find out a place of origin in France is through the charity records, but no trace of them there either. Arguably they could be on the Royal Bounty lists 1730-60 if they came over then (held at the Huguenot Library in London), but these became less detailed after the 1720's. Names are only given for the 'first estate' by the 1750's the landowning aristocratic classes, and even in the 1720's children were not named, and place of origin in France only occasionally given. I don't hold out much hope there either if I'm honest.
If he was born in France between 1730-1760, he should have a baptism record, as you already know even Protestant children were given Catholic baptism, but without a centralised search index, finding him is no easy task. Cannot find any trace of him on French Huguenot sites such as Jean Paul Roelly's index.