I have a Fabia with the 1.6 TDI (remaped), and during the whole of my studies I was doing 400Km a week (2x200km) of highway, was a perfect engine for that as I consumed less than 5L of fuel per 100km. Also did quite a few long trips with no issues whatsoever, for vacations in Austria or even moving (meaning much more stuff loaded in it) to the UK and now to Czech Republic (I'm originally from France)
However now that I am in Mlada Boleslav doing my end of study internship I do only drive short distances so i'm quite worried for it. I don't know where I'll work after my internship but I know that I want to get rid of diesel and finally get a petrol car. They are overall more fun and you don't need to do big trips with them. Would probably keep my Fabia longer if it was a petrol though, it's a great little car.