Cancelling here forfeits the deposit at any notice, accepted force majeure converts it to credit instead of cash, and the fourteen-day withdrawal right never arises.
The short answer first. A cancelled booking does not get its deposit back. Notice buys nothing: two hours of warning and two weeks of warning end in the same place. There is no sliding scale and no grace period to aim for.
The spending happens at the yes. When the office accepts, a therapist's window is locked, other requests for it are refused, and the coordination and travel are set moving. By the time a client thinks of cancelling, those costs are already sunk, and an early message lands after them, not before.
Two grounds only. A government ban on operating, or a serious illness that makes the booking impossible. Each claim is read on its own facts. An accepted one turns the deposit into credit toward a later booking; it never turns into cash. A diary clash, a meeting that ran long, a mild cold, a flight the airline moved, or second thoughts: none of those qualifies. They are cancellations.
The returning client's same-day hour, or a request taken while she was already in the taxi. Cancel one and the costs were committed all the same. The office then asks, after the fact, for a cancellation-collateral payment equal to the deposit that booking would otherwise have carried.
A session the client ends early is not refunded, in whole or in part. A therapist may end one at once, without refund, where her safety or consent is compromised.
The Wet Koop op Afstand, the Dutch law that carries the EU Consumer Rights Directive, gives a consumer who buys a service at a distance fourteen days to pull out, as a rule. The date-specific-service exemption in Article 6:230p of the Dutch Civil Code removes services performed on a specific date or within a fixed period. A booking for a named hour on a named day is precisely that. The right does not arise, and the house policy governs.
The complete position is on the cancellation policy; who pays half, and how, is under deposit.