teropa,
I'm sorry, I didn't notice that you were posting from Finland.
I'm afraid that the NPPL is a UK National Private Pilots Licence and, if you are medically qualified to drive professionally, then you can use all the benefits of a PPL in UK daytime VFR. If you only qualify to drive privately you can still fly solo or with another qualified pilot.
I am in the process of converting my UK PPL(A) to a NPPL as, at my great age, the medical requirements are so much more relaxed. For example, my Medical Declaration from my own doctor cost me £12, compared to the £85 cost of the full PPL Class 2 medical. The only down side is that I will not be able to fly abroad which, with the new requirements for an ELT, I am unlikely to do any more anyway.
Also, if anything goes wrong with me during the year, my doctor will be the first to know about it and will have the right to exclude me. I will not need to inform the CAA which means that they will usually ground you pending a full report from a specialist which, in the UK, can take a very long time or cost you a lot of money.
I think that there are signs that the EEC might adopt a similar licence.