Thank you so much for all the info on Sarah Foster. Another member has also suggested the same names for her parents and siblings, so I think it is very likely that they are my ancestors.
Thanks also for looking at the Ludders. I already know lots about them thanks to previous research by my father and other family members, but your info has helped to confirm some of it. I am most interested in finding out about Sarah before her marriage.
I must also thank you for pointing me to the LDS website, I had not thought of looking there. A quick search has just given me a possible lead on another ancestor from a different branch of my family.