For the past few days I have been trying to get weather station data interpolated in a map for my country only. I do this as follows:
You haven't plotted the Netherlands.
# Create map
...
# Draw contours
...
# Plot seas from shapefile
sf = shp.Reader(r'/DIR_TO_SHP/shapefiles/northsea')
...
# Plot France from shapefile
sf = shp.Reader(r'/DIR_TO_SHP/shapefiles/FRA_adm0')
...
# Plot Belgium from shapefile
sf = shp.Reader(r'/DIR_TO_SHP/shapefiles/BEL_adm0')
...
# Plot Germany from shapefile
sf = shp.Reader(r'/DIR_TO_SHP/shapefiles/DEU_adm0')
...
# Finish plot
So parts of the Netherlands are filled in with your plotted data, The coastlines are there (from drawing the seas?), but the rest of the country isn't there because you haven't drawn it.
I would steer away from this method of drawing from each shapefile individually, and try to just use basemap for your coastlines, etc. If you must do it from the shapefiles, I would encourage you to define a function that does something like:
def drawContentsOfShapeFile(mymap, path_to_shapefile):
#and use it:
m = Basemap(...)
myshapefiles = []
myshapefiles.append("/DIR_TO_SHP/shapefiles/FRA_adm0")
myshapefiles.append("/DIR_TO_SHP/shapefiles/norway")
for sf in myshapefiles: drawContentOfShapefile(m, sf)