Firstly its not a Qualifying Cross Country, that ceased to exist in 1999 with the demise of the old UK PPL, Group A etc. Its now an experience requirement that forms part of the Navigation Training (The QXC was conducted after all other PPL training and skill test had been completed).
The candidate should be capable of navigating using all available aids in the aeroplane and if that includes GPS then they should have been trained how to use it. If they cannot navigate without the GPS, it will show in the Skill Test where on the first and principle leg it is not permitted.