I gave it a go; the biggest departure seems to be in the seventh verse where the king declares he'll kill both his wife and her chamberlain:

JAMIE

And Jamie he had made a vow
And keep it well if he may
That he would be in merry London
On St. James’s Day

“On Saint James’s Day at noon
In London I will be
And all the lords in merry Scotland
There should ride with me"

Then up spoke Queen Margaret
The tears fell from her eye
“Leave off these wars, O noble king
And keep your fidelity

For the water's wide and it's wondrous deep
From the bottom unto the brim
Me brother Henry has men good enough
England is hard to win”

“Away, away, this silly fool,
In prison let her lie
For she is of the English blood
And for these words she will die!”

Then up spoke Lord Thomas Howard
Queen chamberlain that day
Saying “If you kill Queen Margaret
Scotland'll rue it alway”

Jamie, all in a rage
Said “Away, this silly mome
One shall be hanged and the other burned
When I return anon”

At Flodden Field the Scots came in
Which made our Englishmen fain
At Branxton Green the battle was seen
And there was Jamie slain

And presently the Scots did fly
Their cannon they left behind
Their banners gay were all run away
Our soldiers beat them blind

For to tell you plain, twelve thousand were slain
And that's how the fight did stand
And many was a prisoner took that day
The best in all Scotland

That day left many a fatherless child
And many the widow poor
And many the Scottish gay lady
Sat weeping all in her bower

But Jack with a feather was wrapped all in leather
For his boasting was all in vain
But he had such a chance with a new Morris dance
But he never came home again

And Jamie he had made a vow
And keep it well if he may
That he would be in merry London
On St. James’s Day