Megane Poor Start High Consumption

Those symptoms definitely point to a throttle issue. Has the engine light come on? Sometimes a defective accelerator pedal module can cause those problems too.

No engine light, surprisingly. The accelerator pedal module, eh? Can I check that myself, or does it need a diagnostic tool?

If there is no engine light, maybe check the car throttle. But I would not exclude a defective accelerator pedal module. Given the symptoms and mileage, I'd recommend a workshop. They can pinpoint the cause and save you potential headaches. Better safe than sorry!

Took it to a local mechanic, and you were spot on – it was the throttle valve. New one installed and the car is running smoothly again. The total repair cost was 205€, which I think is reasonable.