One way car rentals are covered in exactly the same manner as a standard car rental. We don’t take individual rental details (apart from dates on a single trip policy) and as long as you have all the car hire paperwork confirming the correct locations, cover will apply as normal regardless of where you collect and return yuor vehicle.
A one way vehicle rental simply means collection and return of the vehicle from different locations. Its quite common and sometimes the only reason for the rental is to get between these locations.
For example you could pick up a rental car at Stansted airport and drive this to Heathrow airport where you drop the car off at the rental suppliers desk, this constitutes a one way rental. There are sometimes a "one way rental" charge applicable for doing this but it depends on the rental provider and locations being used.