Hi, I've looked through my records and cannot find Hannah or Joseph with the dates/places you describe. The Thomerson family originated in Essex, UK and then most of them moved to what is now called East London.Only much later than the mid-1700s did some move to South London and Kent.
There have been a few cases where Thomerson / Thomason / Thamerson have been interchanged and maybe also now with Tommerson. I can't rule out a link, but it seems unlikely at the moment.
I see that the Tommerson / Digby marriage is in the IGI, in St Paul's church, Deptford. I suggest you try to get hold of the microfilm of the marriage and baptism records for this church to see if you can trace this family any further.