Justin,
That's fascinating, and when I looked on the 1851 census I found that Esther's father was indeed
Arie Lieb Barnett, born 1798 in Prussia, Rabbi of the St James Place Synagogue, so that must be the Great Synagogue you were talking about above.
All the siblings of Esther, like English families, had the forenames repeated, so there is an Adelaide a Baron, and of course an Abraham, but also a Louisa and a Jane. That Pleszew looks a fun place to visit, from a website of the town in Poland. My wife says that maybe we are related to the President of the United States!!
Abraham and Esther were born in Prussia, but the others were born in London, that was Louisa aged 14, so 1837 or so. Now where do I go from there to discover arrival dates in GB from say Poland/Prussia, perhaps Rootschat Poland would help maybe, this is all very new stuff altogether.
Tom