Hi Amanda,
I'm a descendant of Jane Davison's brother, Thomas Pratt Davison. I've got as far back on the Davison side as I can and have found nothing about Emily Davison. I believe you've been in touch with my mum's cousin Anne. I have some photos of Thomas Pratt Davison and of the Oliver children, who were my Gran's cousins. I also am pretty sure that I have a photo of Thomas & Jane's mother. Let me know if you're interested in copies.
Rachel