I also had a similar experience to John last year but at Blair Atholl. They could not find my parcel until they checked the post that was about to leave.
They had marked the parcel as "Not known at this address, return to sender"
It was marked as Post Restante and my name but they appeared to be ignorant about the services that the Post Office actually does offer.

Whenever I read about the Poste Restante, I have to smile at using a French term for the Royal Mail.

I have sent parcels this way, too, but also put at the bottom under the address post code

PLEASE HOLD FOR (name), ARRIVING ON (date)

As others have said, it’s helpful to call and tell them a package is coming but it can be hard for those international challengers to do this.

Do ensure the post office will be open on the day you’re arriving, and the hours. I’ve heard of people getting burned this way, too, having to wait to the morning to get their pkg.