Thanks for your reply. I had already taken a look at the resources you mentioned and also noticed the discrepancies with the dates. For other branches of my family the IGI is usually only a year off (presumably from getting ages from a census and not knowing when the birthday was) but for some reason a lot of the PITHERs seem to be several years out. I expect somebody guessed a lot at the dates.
What I was wondering is if you know of a definite link between the Crondall PITHERs and the Shinfield PITHERs. I suppose there must be one because the distances are not so great. I assume that the PITHERs originate in Berkshire as that's where most of them seem to come from. Do you know of a PITHER who moved to Hants?