Searched, and found this in 'The Dynasts' (Thomas Hardy) although I am sure I recall longer version from school.
I realise it's not Nelson, but the cause of battle is much the same!

Nigel

We be the King's men, hale and hearty,
Marching to meet one Buonaparty;
If he won't sail, lest the wind should blow,
We shall have marched for nothing, O!
Right fol-lol!

We be the King's men, hale and hearty,
Marching to meet one Buonaparty;
If he be sea-sick, says "No, no!"
We shall have marched for nothing, O!
Right fol-lol!

The above is as found on the net.
I remember learning it in school as:


We be the King's men, hale and hearty, - oh.
We be the King's men, hale and hearty,
Marching to meet one Buonaparty;
If he be sea-sick, says "No, no!"
We shall have marched for nothing, O!
Right fol-lol-lol-o!
Right fol-lol-lol-o!
Right fol-lol-lol-o!
Right fol-lol-lol-o!


Same war, but land based, not a sea battle.

Cheers
Nigel