I just replied to your email a couple of minutes ago, but here on the forum you raise a few further questions, so here goes!
Yes, I can take us further back two or three generations from Seth and Agnes.If you look on my web site it gives the "bare bones" but I'll send you more as a pdf email attachment.
I'm interested in the "Biggins" origin of Seth.Where did you get that from?Biggins is, of course, a small hamlet on the fringe of Kirkby Lonsdale.Some later Fishwicks seem to have lived there for a while, but I'd never connected it with Seth.Casterton was his home patch, although as you'll see from the file I've just sent you, I've never conclusively proved that Thomas & Lydia were his parents (although I believe that they were!)Seeing that you have made the Seth-Thomas/Lydia link independently I'll be very interested to see how you arrived at it.
Thomas, by the way, was the son of an earlier Seth.He was born in the Kirkby Lonsdale area, and I believe that this Seth was the son of yet another Thomas, and was born at Dilworth (Longridge)and baptised at Ribchester.That is as far as I've been able to go, and am currently working on the parish registers of the Preston area to see if I can find how this Thomas fits into the several Fishwick strands around there.
You mention a Richard, born 1665.Was he in the Kirkby Lonsdale area, or further south in Lancashire?Where did you find him?