By "national" songs I mean the kind of composed parlour and minor art songs that used to be thought typical -by the cultural establishment- of the various nations of the British Isles. It's the usual term. Exactly the things that Cecil Sharp and other progressive educationalists wanted to replace in school curriculums with genuine folk songs. Greensleeves, Cherry Ripe and (though it's a grey area, which is why I said "probably") John Peel aren't folksongs by generally accepted definitions. Ben didn't ask for typically English songs (or we might be looking at things like Tom Bowling or Drink to Me Only) but for typically English folksongs.