“As I understand it, (and I may well be out of date ) one of the "benefits" of the further training and exams to upgrade a license from NPPL Microlight to the NPPL SSEA is that you can no longer fly to Europe ”
This is not true. The NPPL is only valid in the UK, but it does not actively state that you cannot fly in Europe, just that it does not give you this right. Exactly the same situation existed some years ago on the MPPL. Lots of pilots asked for permission from various European countries, and it was being given 99% of the time. Eventually a deal was struck and the MPPL was accepted in Europe despite not reaching the international standard.
There have been reports of several NPPL/A holders requesting permission to fly in Europe, and getting it. The New R/EPPL will be along in <2 years and will give you this as a right.
The PFA permit rules are the same, and the same repeated request for permission caused a more general approval to be agreed.
Rod1