Is the petrol tank bigger than the Fabia? I have a friend who swears blind that the Scala tank. is a lot bigger than his 2022 Fabia. 

Certainly new Octavia has 10% smaller fuel tank than the Mk3.

Scala has 50l fuel tank I think like the Mk3 Octavia, current Fabia has 40l -45l depending on version. I did notice that Skoda seems to hide/omit fuel tank capacity in recent brochures other than the larger cars.

For range at (moderate) speed, best cars were Roomster and Rapid diesels, good old 55l + 9l vented capacity fuel tank. From Mk3 cars onwards, the only long range non-SUV Skoda seems to be the Superb, Octavia got cut from 64l vented to 53l vented, Fabia's range got hit even worse. If only engine fuel efficiency followed...

An Owners manual will tell you are cars specification / capacities, online manuals.