Thank you for your response. The earliest member of the family that I have traced in England is Noah (Nachum) Edward Lewis who would have been born about 1760 (very approximately) - whether in England or Holland I do not know. He died in 1830. His eldest (known) daughter, Sophia, was born in 1790 in England. His wife, Frances, was born c1767 from her age at death.
The information suggesting the Loew ancestry came from a book about his grandson. "George Henry Lewis belonged to a family of Sephardic Jews from the Netherlands who settled in England in the eighteenth century, afterwards changing their name from Loew to Lewis"
As you can see this is a very faint clue and I have no idea of whoever it might have been that left Holland. (Amsterdam was a mistake - confusion with another later ancestor, Werner Mähler - my apologies). I only hoped that some Loew descendant might be familiar with the Lewis family.
Many thanks for your interest.