What is the right behaviour now?

Accelerating is the right behavior here because once you have a clear “go” (for example a green temporary traffic light and a prescribed bypass around the obstacle), you should pass the danger area decisively and without hesitation. A short, controlled acceleration helps you clear the narrowed section faster, reduces the time you spend in a potentially risky zone (roadworks, workers, cones), and is especially important if you have to use the oncoming lane briefly to pass an obstruction. That also makes it easier for any oncoming traffic and reduces the chance that the situation changes while you are still alongside the obstacle.

This does not mean “speed up as much as possible.” You may only accelerate within the posted speed limit and only if the road is actually free and it is safe. In roadworks, you still drive with increased caution, keep enough lateral distance to workers and equipment, and be ready to slow down again if something unexpected happens.

Why the other ideas are wrong in similar questions: maintaining the same speed can be too hesitant if you are supposed to clear a bottleneck promptly, and waiting to accelerate until a speed limit ends misses the point because a speed limit does not require you to keep the exact limit; it sets the maximum. The key rule of thumb is: in narrowings/temporary lane diversions, proceed smoothly and decisively, but never exceed the current speed limit and never accelerate if it would reduce safety.