Use:
Alloy Wheel & tyre fitment calculator - it calculates inset, poke, speedo error, tyre stretch and loads more.
willtheyfit.com
ET40 offset will stick out approx 17.5 mm over stock
Cupra 19" alloys. ET35 offset will stick out 22.5 mm over. People generally use 12mm spacers on front and 15mm rear, so will be tight to the arches.