Firstly, thank you so much for your prompt replies.
Thanks Dave, for Leafield lead, which I'm going to pursue.
Thanks Sue, I found the Old Bailey reference earlier. Please tell me what sites you use to find census refs. I use Ancestry.com so I had to do a lot of manual searching through census records to get the right page for 1851, but eventually found it. I don't think it is possible to look up a specific reference in the form which you gave me. I haven't yet looked up your suggestion for 1841, but I do know that Ann Spratley's mother was also Amelia, so it sounds highly likely.
Thank you so much. I may well ask you for more help with other brick walls in the near future, e.g William Wiggins' parentage.
Best wishes,
Judy