Thanks for the thoughts so far folks. It is conceivable that cousins might have married women of the same name and had a child with the same name within a short space of time.
I notice on the image that all of the children have no birth date. Was this not recorded I wonder, and only the Christening date recorded, or were they Christened on the day they were born?
If they were Christened on the day they were born, then for Bert's thoughts, there is only an eight week gap between Christenings, so it would not be possible for Jane to give birth again, unless the first birth was a good while ago and never registered.
If Bert's theory is correct, then there should be a corresponding death record for the first Sarah. Whether it was recorded before or after the second Sarah was born though....
As a footnote, I have just been looking through the Bishop's transcripts. One of John and Jane's other children, John, was born in May 1810 but not Christened until August. Actually, thinking about it, the first children were Christened, the later ones Baptised. Different families, Catholics and Protestants??

Names - Orrett, Orritt, Ross, McCabe, Keeley, Bullen, White, Leatham, McKeon, Bilsbarrow, Yates, Sennett, Sinnett, Traynor, Ashton