Seat Ateca Engine Light and Fuel Consumption Issue

That sounds suspiciously like the issue I had with my old Volvo! Check engine light and increased fuel consumption are classic symptoms. It could very well be the VANOS solenoid. The VANOS system controls the valve timing, and if the solenoid is faulty, it can't adjust the inlet camshaft properly. Have you checked for any engine misfire codes? A faulty timing chain could also throw similar codes, but at that mileage, it's less likely than a solenoid issue.

Engine misfire codes? How would I check for those? And if it is the VANOS solenoid, is that a difficult fix?

Yes, misfire codes will show up when the engine isn't running smoothly. You need an OBD2 scanner to read the diagnostic trouble codes (DTCs). As for the VANOS solenoid, it's usually a straightforward fix – unplug the old one, unbolt it, bolt in the new one, and plug it back in. However, if the problem is with the wiring or the VANOS unit itself, it gets more complicated. Given the symptoms, and the potential for damage, it's probably best to take it to a workshop. 250€ sounds about right for a solenoid replacement if that's indeed the problem.

The workshop confirmed the inlet VANOS solenoid was the issue. A new one was installed and the engine light is off. It runs much better now. Thanks for the advice!