Were you also entering or leaving Italian or Portugese airspace? Because...
Italy and Protugal, have north/south FL "orientation". That means, that some of their neighbouirng countries (ATCs) will probably have to assign a different (non-standard) FL before the border (airspace border).
Also, like mentioned above, FLAS are the reason. Due to small portions, corners of airspace here and there, where many routes are crossing, merging, converging, from east to west, and south to north - it is sometimes better to have non-standard FL at least until the acft leaves that area. It is a tactical agreement between, ANSP, for safety and efficency.
Guy D', non-RVSM in W Europe?
