Some great advice there guys
It happened to me once where they guy was trying to turn me into a handy man, after I fitted a power shower in his en suit, then tiled it.
Just because I had a tool box of spanners etc, he though I was up for any work around his house that needed done. When I refused, he threatened not to pay me for the shower/tiling that I had done.
The fact that I then took photos of my work and threatened him with the small claims court as I walked off soon persuaded him to cough