I rent a car at £1
from Mérignac to Biarritz - Pays basque ...
Rent one-way from your city of departure and the airport of Biarritz - Pays basque
.. which I use
during 24 hours...
You have 24 hours of rental with enough miles to make your move to the Biarritz - Pays basque airport.
... And I leave
directly at the airport
As for a conventional rental, you drop the car directly to the Biarritz - Pays basque airport parking.