Okay, so when I glanced at the signature, I thought I saw an Italian name in there somewhere! But, having lived in Italy a bit, I do that from time to time (yes, it sounds unusual)...Oh and perhaps an amersand
So for the heck of it...I tried Florence Casartelli. And, the following search result appeared:
http://www.cartedevisite.co.uk/studios/england/The link has information of photographers from Great Britain and Ireland from 1840-1940. There is a Croft Studio listed as well as an Ashton.
As far as photographers in England, there are two which caught my eye: Florence Cary and J. Casartelli. So maybe there was some extra curricular activity going on in the workplace and the two photographers hooked up! Based on this speculation, I believe the miniature is perhaps by Florence & J Casartelli.
The photography site does offer research options, but they only accept PayPal if you have an interest to investigate the miniature on ivory a bit more!