A friend pointed me to the Willison Family Tree website http://www.willison.org/ which has Willisons in Scotland going back to about 1625. I have yet to find a connection to my family but there are two things in my favour.
On the Willison website it says that “by tradition the eldest son was named John” and I have four generations of John Willisons, the eldest sons. Also they were in Scotland as were my ancestors. And so the hunt continues!!
Here is a post I wrote previously about the meaning and history of the Willison name. http://kyliewillison.blogspot.com/2010/06/surname-database-willison-surname.html