In both the Seat and M135i's manuals, a run in period is still strongly suggested with a mix of driving conditions for 1,200 miles and 1,500 for the BMW. I think it's still worth the run in as all the components are tight, therefore not breaking in could cause excessive wear and tear on components (people are free to do what they like though, most dealers say it doesn't need running in).
For the
Cupra 280, are those Dyno figures before or after the calculation of a 15% drivetrain loss? As considering a remap, but shalt bother if it's already producing over 300 ponies