Frances,
I recently received a PDF of descendants of Ffinlo Kewish from a contact in Lancashire and the Ballagawne Kewishes are on that.
I'll have a look back at that - either one of the sons or another Kewish was shown as a builder once I matched up the census with the person - but I tended to think he was a bit young to have built the house at Willow Terrace -however, I'll double-check.
The 1888 Will might be helpful as it could list property. I'll work on that too.
Thanks again.
MoragC