According to the BVRI (and I see that Bythorn baptisms have been extracted onto the IGI at
www.familysearch.org so you could have checked them yourself) there are no Banks baptisms in Bythorn from 1606 until presumably your James and Ann baptised children 1786-98 as follows
Jane 25 Jun 1786
John 23 Sept 1787
James 8 Mar 1789
Mary 17 Apr 1791
Thomas 3 Mar 1793
Sarah 26 Aug 1798
James Banks married Ann Curpin at Bythorn on 27 Oct 1785, both otp
The only previous Banks marriage was that of Mary, otp, to William Boyfield on 8 Oct 1771
I only have access to Banks burials up to 1800, which can also be accessed on the pay per view site at
http://www.familyhistoryonline.net/which are
Sarah 3 July 1766
Sarah 3 Mar 1775
Edward 4 Dec 1787
Jane 27 Mar 1795
Sarah 27 Mar 1795
There was only one marriage 1754-70 in Hunts of a Banks to a Sarah:
1760 John & Sarah Swepson at Hail Weston
I cannot see a marriage of an Edward Banks in Hunts
Bythorn is also very close to the Northants county boundary so it's possible they came from there.
Regards
David