To help the discussion about whether there was a Lancashire,
Charles Stewart, etc. in the ballad, here's the text from another
early version of Bonnet so Blue, also from the Bodleian Library.
Bodleian Library Broadside Ballads: Harding B 11 (393).

Bonnet so Blue

In Liverpool town, in fair Lancashire,
I lived in splendour and free from love's care,
I rolled in riches, and sweethearts not a few,
I'm wounded by a lad and his bonnet so blue.

There came a troop of soldiers, and soon you shall hear,
From Scotland to Liverpool, abroad for to steer.
There is one among them I wish I'd never knew,
He's a bonny Scotch lad and his bonnet so blue.

His cheeks like the roses, his eyes like the sloes,
He is handsome and proper, he kills where he goes
He is handsome and proper, & comely to view,
He's a bonny Scotch lad, and his bonnet so blue.

When I go to my bed, I can find no rest,
The thoughts of my true-love still runs in my breast
The thoughts of my true-love still runs in my view,
He's a bonny Scotch lad, and his bonnet so blue.

Early one morning, I arose from my bed,
I called on Sally, who was my waiting maid,
To dress me as fine as her hands could do,
I'll away to see the lad with his bonnet so blue.

She was instantly dressed, and parade did attend,
She stood with impatience to hear her love nam'd
Charles Stewart they do call him, my love did renew
Once a prince of that name wore a bonnet so blue

My love pass'd by me with his arms in his hand,
I strove to speak to him but he could not stand,
I strove to speak with him but away then he flew,
My heart did go with him and his bonnet so blue.

She said, my dearest laddie, I'll buy your discharge
I'll free you from a soldier and set you at large,
I'll free you from a soldier if your heart be true,
And you'll ne'er wear a stain on that bonnet so blue.

He said my dear lady, you'll buy my discharge,
You'll free me from a soldier and set me at large ;
For all your kind offers I am oblig'd to you,
But I'll never wear a stain on that bonnet so blue.

I have a dear lass in my own country,
I'll never forsake her for her poverty ;
To the girl that I love, I'll always prove true,
And I'll never wear a stain on a bonnet so blue.

I'll send for a limner, without more delay,
To draw my love's picture that I may it see ;
I'll set it in my chamber, keep it close to my view,
And I'll think on the lad for his heart it was true.

I tried to copy the lyrics accurately, including the original punctuation
and grammatical errors (e.g., "thoughts … runs"), but in case I made
a mistake you can see the original at the link at top of this post.