Hi Tom,
Thanks for this information, I think I have some of the matching details here, however I was not sure I had it correct so didn't send it before. They're just details I've found searching through the IGI etc and so I wasn't sure if I hadn't taken a wrong turn (as I have done once before) or whether I had it right. Happily, it seems I've been on the right track after all.

I have Sarah SMITH marrying Benjamin Nicols BENNETT on 7/5/1854 at St Dunstan and All Saints, Middlesex. I have 4 children's names which all, fortunately, seem to tie in with yours - Sarah Amelia, bap. 12/2/1854, Eliza Martha (who must have been your g-grandmother) bap. 27/4/1859, Richard George bap. 9/8/1861 and Sarah bap. 1864. The first 2 were baptised in Poplar, MDSX, the last 2 in Limehouse, MDSX.
Can you tell me how the line has progressed further from any of these people? I'd be interested to know about Eliza Martha's descendants at least. You may want to send those details off-list, depending on dates, etc.
Looking forward to learning more, as I'm sure the others are too.
Cheers,
OzJen