Thanks everyone. So in short, in my market (and in Germany, as far as i know), when you get a Golf with Nav, you also get a USB stick called "CarStick" that goes into the USB slot behind the gear shifter. It has a SIM card in it (in my market, 10GB internet a month for 3 years), so you can even create a WiFi in the car (via the WLAN menu of the car) so your mobile devices can use those 10GB of internet.
However, Golfs have only one USB port, unless you have specified the "wireless charging" option, that adds a wireless charging capabilities of the cubby behind the gear shifter. Then, you get a 2nd USB port somewhere (i think under the arm rest). So, if you do not have that option, as many do not it seems, it is impossible to both use the CarStick for the internet AND AndroidAuto/CarPlay.
So, I was wondering, if UK cars have internet without any additional sticks and whatnot, then I thought it would be possible to get the SIM card from the CarStick device and put it in the car somewhere to use the internet. But i guess this is not the case.