I presume this was glass made to specification?
Did you agree cancellation rights?
Ok but you agreed to it verbally?
That is not good news I'm afraid.
Come what may, you agreed verbally. A verbal contract is as good as a written one. It really doesn't matter whether you signed anything or not.
Unless you agreed cancellation rights none will exist. This is a contract exempt from the doorstep selling and other distance selling arrangements because it is made to your specification.
Unfortunately therefore you will be liable for the work even if you don't complete with them.
If they have made the product then they cannot sell that elsewhere so I'm afraid the full amount would be due.
I'm very sorry but that is the reality.
Can I clarify anything for you?