The stereotypical American secular Jew would love the ideal of the Lib Dems. The reality of the Lib Dems and the difference between secular American Jews and British Jews would explain why the LD share was so much lower than I expected.
I would be interested in your views as to how you consider Jews of the two nationalities to be different. I have never thought about that before. Granted the Tories these days have a more secular - and less Christian-centric - image than the Pubs do these days, but you are suggesting it is less about the image of the parties, and more about the differences between the two groups of Jews themselves.
I believe British Jews have long favored the Tories. I'm out of my depth on this, but Thatcher represented a Jewish constituency (not that it mattered that much which one she represented) and she liked Jewish businessmen for representing the business side of Toryism rather than genteel paternalism she loathed. You just didn't have the same history that led to Jewish identification with the Dems that you have in the U.S.
I feel I know very little about British Jews other than where they live and roughly how they vote. If I got anything wrong in the above paragraph someone will come along and correct it.