Amazing, thank you so much Ciderdrinker, I didn't have either of those 2 daughters. That's very exciting. I've located Sarah and husband Joseph in the records, I can't see yet which daughter married JC Lyons but I'm sure it'll come to light quite easily. That's such brilliant new information
I had just started to stall slightly, but you've jump-started it again!!
Other interesting things in the meantime I've discovered through Synagogue Scribes:
The 2nd marriage record of Jacob Issachar Cohen showed that the bride's name was Sprinsi (Shprintsa being her Hebrew name) her family name was Leo and she was the widow of Doctor Leib Kassel (or Cassel). She married Jacob Cohen on 9 Apr 1813 at The Great Synagogue in London.
Jacob's father's Hebrew name was Yehuda (Judah) Cohen and he was a privileged member of the Synagogue (I've copied that across, I'm not sure what it means but I've asked!). So that all chimes with the theory that the 2 Judahs were cousins, named after their grandfather.
Godfrey's Hebrew name was Gotchlik, I guess that's where Godfrey comes from (I thought it was a slightly odd non-Jewish sounding name). And one of his daughters Esther Eliyakum Goetshlik Cohen also had it in her name.