What a shocker!

You're in Victoria right? Investigate your complaint options - Consumer Affairs Victoria - Building & Renovation - and tell the company that you'll be .

I agree with Spring angel, the youtube / leaflet option sounds like it will just cause problems for you, not them. Official channels doesn't necessary mean legal action, you go through the complaints process.

As for what discount to ask for... hmm that's a tough one. Maybe one third off, which should represent their profit margin for the job.

Good luck and have a merry a christmas as possible!