The last two (by C Mair and C Fox-Smith) are not about England or St George, but refer to Britain as a whole, so are really more suited to 24th May rather than 23rd April. I still remember snatches of a song we sang on the morning of 24th May (Empire Day) at our infants school back in the early 1950's.

We have come to school this morning
On the twenty-fourth of May
[Can't remember this line]
Because it's Empire Day.

Empire Day was a half-holiday for us then, so we had no school in the afternoon.