Lunch and a bath in about two hours
Arrive around 11:00 and both the restaurant (11:00–14:00) and baths (11:00–20:00) are open. Eat first and bathe afterward, then head straight back to the car.
Park → restaurant → baths → shop → depart.
On Thursdays the baths open at 13:00; the station closes on the third Thursday (or the preceding Tuesday if that Thursday is a public holiday).