As can be seen from the recent posts, it is really complex!
Every recommendation has to be personally tailored, hence I - as someone who runs a NPPL (M) flying school - suggesting that the best route for the original poster
might be the full-fat EASA SEP.
But many "rules" can be overcome.
Here is one Strathaven chap flying across the USA in the ultimate permit to fly aircraft - no doubt here that it is a microlight - with an NPPL(M) !
www.c2c2c2018.com