"Most English nationalists/separatists do use the song Jerusalem, which is another thing that makes my skin crawl (because of its Anglo-Israelite and potentially anti-Semitic implications)."
Jerusalem is a great song, and a Christian hymn... and any fan of Monty Python would have heard it a few times in various skits they did.
I don't see how it is anti-semitic, it was written by William Blake, who wrote of "dark satanic mills", a romantic of the early industrial age...
http://www.engelen.demon.nl/chariot.htm
JERUSALEM
And did those feet in ancient time
Walk upon England's mountains green?
And was the holy Lamb of God
On England's pleasant pastures seen?
And did the Countenance Divine
Shine forth upon our clouded hills?
And was Jerusalem builded here
Among these dark Satanic mills?
Bring me my bow of burning gold:
Bring me my arrows of desire:
Bring me my spear: O clouds unfold!
Bring me my chariot of fire!
I will not cease from mental fight,
Nor shall my sword sleep in my hand
Till we have built Jerusalem
In England's green and pleasant land.
If you *really* want to offend the Muslims,
wave the Saint George's flag on his Saints day,
singing "Onward Christian Soldiers".
I've never watched much Monty Python, being a prude and all.