It sounds like the person who booked you in was just tring to get you off his back, then once you were gone they forgot to book the tint guy. Seems to me that they may be feeding you BS. Could just have run out of time on the other issues though. I don't know about other dealers, but where I used to work there was only a skeleton staff on saturdays and the people who were there didn't really want to be so it was a pretty unproductive and lazy day. The mechanics I worked with only wanted to do routine servicing on saturdays.
The money side of things won't make any difference. It would be very harsh if retail labour rates went up on a saturday to cover the increase in pay for the mechanics! Generally dealerships just have to absorb this cost as it's more cost effective to do so than to shut on a saturday or not get any work in because the labour rate is higher.
Best off taking it in during the week and saying they can keep it as long as they need provided you can have a courtesy car.
If there are problems that may be difficult to pinpoint or get a satisfactory fix immediately then this will help you both out.
Any Holden dealer is obliged to address the warranty issues. They all get paid whether you bought the car from them or not. As far as I know the selling dealer wouldn't be penalised for warranty issues with the car. It should just be paid by Holden and that's the end of it. After all it's Holden that build the cars, not the dealer. Pretty unfair to financialy penalise the dealer for something that isn't their fault and is really beyond their control to prevent happening. That's how it worked with Vauxhall anyway.
One thing to keep in mind is that there may be lower mileage or time limits on the manufacturer's warranty for certain items on the car. With Vauxhall, windscreen wipers were only covered for 1250 miles, brakes 5000 miles (IIRC), battery 12 months, etc so it's worth checking to see how long each item is covered. The warranty administrator at the dealership should have a comprehensive list they can show you.