Firstly thank you to all who have commented, but especially to Spidermonkey et al for braving the elements on my behalf- very good of you. My starting point that I am fairly confident about is a Helen Winston (my 5xggm) christened in Blakemere 14 may 1736 to a James and Elizabeth. Purely on a speculative basis I had then assumed that this James was the one christened in Madley 28 Sep 1701 but as you have now pointed out there are other contenders, not least the one named on the floor slab. Not sure how I will resolve this lot but I have been in touch with the College of Arms to get a transcript of the 1683 Visitation that has a pedigree of the Winston's of Blakemere- maybe that will provide something interesting.
Nigel