Hi Richard, Graham here - I run the Ten Oaks site (with lots of help from people who do far more research than I do!). Glad to hear you have found the site useful.
I would think there is a fair likelihood of your Leith family and those of 1881 being connected, as the Tocher population in that area wasn't particularly high. However, your grandfather is a bit outside the date range for which I currently have much information. I would suggest that your next step needs to be track down your grandfather's birth, and obtain the birth certificate - this would supply his parent's names. Let me know if you need practical advice on that. Do you know roughly when he was born? You mention that he came from "down south" - Scotland or England? The England 1901 Census has just one Charled Tocher (born Cheshurst Herts) but aged 35, so maybe a bit old to be yours? If your grandfather was alive in 1901, you could also try a search on the Scotland 1901 Census - available now at http://www.scotlandspeople.gov.ukhttp://www.scotlandspeople.gov.uk
Clan/tartan connections? Not as far as I am aware. The Tocher's home in Aberdeenshire is outside the Highland area, so unaffected by the clan system.
Do keep me posted on anything you turn up - anything to build on what we already know of the family's history is welcome.