Mark 1, part-FCL and part-MED are all detailed at
http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2011:311:0001:0193N:PDF.
MED.A.30 Medical certificates:
"...holders of a private pilot licence (PPL)... shall hold at least a Class 2 medical certificate"
Hence, no valid medical certificate means no valid licence. The quote in one of my previous posts was taken from the CAP804 (non-legal), but the above quoted paragraph is from part-MED (law).