All NPPL training (which includes renewals) ...............
The requirement to be assessed or mandated for renewal training by a ATO/DTO is subject to EASA and does not apply to the NPPL. The lapsed NPPL does not require a course completion certificate for the 'Renewal' test. Further training for renewal is not required, there is no course, so it follows that any instructor, anywhere in the world, can be chosen by the NPPL holder for their training as they see fit. The Examiner can be as Whopity has identified.
Note: the NPPL GST comprises general handling only and not cross country navigation. Should be completed comfortably within the hour.