Hi Dave
I too am researching Clack's from Broadwell. I wonder if you have managed to get back any further than 1759? My earliest Clack is Charles. I know he married Mary Simpson in 1759 at Kencot and that he resided in Filkins prior to his marriage. They had two children:Thomas, baptised in Kencot in 1759, and Edward, baptised in Broadwell 1761. There is a burial for a Charles in Broadwell 24 Mar 1784 that could be my Charles.
The only thing I can't find is his baptism and without that I can't find his parents. Your posting was in 2003 and I'm hoping you have had more luck than me since then.

Regards

Maureen