I recently bought Senior Offspring a 12-entry package on PP. She is studying in Manchester so flying Finnair makes sense for us and her, and having PP allows her to use a lounge once each way and works out considerably cheaper than paying for access to the AY lounge.
Ian, I hate to rain on your parade, but MAN is the only airport where I regularly get denied entrance to the PP lounges due to overcrowding.
Unfortunately, access is ‘space available’ and it often isn’t.
I’m not aware of any legal redress, you may be.