It was great to get your message. Thank you so much for the info. It came exactly at the right time. I had found the marriage of a Sophia Tumber with possible spouses Samuel Baker or George Divers through the Free BMD (March 1859) and requested the certificate from the ONS. I have just had a reply saying the reference was incorrect - rather disappointing. On re-checking the Free BMD I find that now Sophia is in the September quarter of 1859, whereas Divers is in March. As you have Sophia marrying an Edward Diver in July, I take it that George was a confusing red herring -still somewhat strange having that surname though.
Regarding Sophia's father George, I have a death certificate for him - 19th December 1839 of scarlet fever aged 32. He had been shown as deceased on the birth certificate of his daughter Louisa - 29th June 1840. I don't know if it was obligatory to put "deceased" where appropriate. (I have that problem with my great-grandfather who married Ada Tumber. He seems to have disappeared when his wife died but appears on his son's marriage certificate not as deceased.)
I would be very interested in making contact with Ron Tumber as there is a chance we are distantly related. I have been in touch with a few Tumber researchers and as you say they do mostly originate in Kent. So far I have been unable to make a connection with my line, which is predominantly female. I didn't consider Sophia having another child taking her name so this is an exciting development.
May I ask you if you have any info on C(K)atherine Elizabeth Tumber - marriage or death 1900 onwards? She would have been one of Sophia's granddaughters, sister to my great-grandmother Ada, but doesn't feature in any family photos so we are curious to know what became of her.
Thanks again for your help. I am living in Germany at the moment so haven't been able to get to the FRO for a while, and as the IGI doesn't seem to cover my Tumber parishes, I wasn't making much progress. It was really a great boost to get your message!