Penfold Family Genealogy Forum
My ggg grandmother was Sarah Penfold, also from Surrey but I believe my Sarah is the one born in Ashtead, given the proximity to Epsom, where she married.
I recalled seeing details on your Sarah on the IGI. You say you are looking for siblings. You probably have already checked but just in case if you log on to www.familysearch.com tab "custom search" and then click on IGI - enter the parents names and you will get 7 siblings of Sarah born between 1766 and 1785, all born at Newdigate.