Hi and and a warm welcome to Rootschat.
There seems to be a lot of doubt here .... "am reasonably certain" " I think..." etc
It is really a good move to confirm each step for sure before you move on the next one, otherwise you can waste an awful lot of time and money following completely the wrong family (oh yes, a lot of us know from experience!)
So, starting with grandma Jane.Have you got her birth cert to be sure of her parents names and mothers maiden name? Have you found the family on the censuses to find years and places of birth for those parents? Using the maiden name as a help, have you found Thomas and Mary's marriage? In turn that cert will give a father for each of them (hopefully) and an occupation.
If you need help searching at any stage you will find everyone here very helpful.
Do let us know what you have for sure with evidence, and we will try to help with the gaps