I'll just add a little more info here that I've discovered with my own S3 8V.
Undoubtedly, if you are lifting the car with a single point jack, then the manufacturer provided jack seams are the correct places to use the jack, scissor or trolley.
Onto the lifting points that are meant to be used with a 4-point lift:
With my particular car, it arrived with the rear rectangular jack pad already installed
It also arrived with the front jack pads already installed, and the plastic cover pressed into the centre of the jack pad (as in Post#68)
I am unclear if this is how the car left the factory, or if the 4 jack pads were installed at PDI.
(On the production line, the car cradle fits directly into the bodywork at those points, no jack pads)
The rear rectangular jack pads are pressed into the rear chassis rail, and if you grab it, you can "wobble" it about using some force.
The front jack pads (in my case) are hidden above a removable plastic panel, the plastic panel presses into the centre of the jack pad. The plastic panel looks like it is supposed to stay, even when used with a 4 point lift, as it seems to have strenghtening ribs moulded into it, and has a circular locating hole, for the peg of the 4 point lift.
Given that it is plastic, and given that you're not supposed to use these points for a single point lift, it's fair to say that I'll only be using these points when used in conjunction with a 4 point lift, to spread the load. I don't think I would like to trust that front plastic lift point on a single jack.