I don't want to contradict Mr Trilby however I think his answer maybe a little bit misleading, I apologise now if I am wrong of if I have misunderstood his reply.
Firstly, the Skoda Connect phone app does not need you to add SIM card in the car, the app communicates directly with the car with no need for you to add an data connection. It will give you loads of information such as mpg, where you left it, Windows open, mechanical updates etc. You need a licence to access this, first year is free but subsequent years are chargeable (ÂŁ35 PA last time I looked).
What I think Mr Trilby is referring to is the infotainment system connect portal which does need a data connection, this is for traffic updates, map updates, navigation routes sent from the connect phone app etc..
You can use an additional SIM for the data connection of the infotainment system, wherever you go for that is up-to you. I however I use rSAP on my phone (business phone connection) so it uses my handset data for the infotainment (no need for SIM in car). Only point I will make is not all phones support rSAP, older Android and iPhones don't I believe.