Forgot to mention in my previous post about the phone calls. As others have said, they plague you with them, and they clearly sold my number to other companies too because I started getting lots of cold calls despite being with TPS and usually not getting anything of note.
No matter how many times I told the window company 'No', including words such as; never, no way, clown, rip-off etc, they still kept at it until I found the solution which worked immediately and has worked with other businesses since:
"If your company ever contacts me again I will start to post very negative reviews of your business on the internet"
Works brilliantly.