Thanks Geoff
I think you're spot on with this one

I have a Susanna Martin Beeston baptised 1785 in Holbeach daughter of William & Elizabeth Beeston.
Also a Susanna Wellbanks Beeston baptised in 1782 Holbeach.
I've just found on IGI Susanna Martin Wellbanks baptised 1772 in Fleet daughter of Thomas & Elizabeth Wellbanks - so both Elizabeth's marriages they had a daughter and gave Elizabeth's maiden surname (Martin) to both daughters as a middle name.
My only query is Elizabeth & Thomas Wellbanks baptised Susanna Martin Wellbanks 24 Jun 1772 but then in Sept 1772 Elizabeth married William Beeston - am I missing something obvious?!
Regards
Sally
ps. Which marriage index do you have that covers this area? I think I need to purchase a marriage & baptism index!