The "I'll sit down..." verse is a good example of what is known as a floating verse in that it seems to show up in many versions of different songs. It shows up in the version of "Black is the colour of my True Love's hair" as sung by Niamh Parsons.

On the subject of Lango Lee, I've never heard of that term being the Irish for penis, but the word "Langer" tends to have that meaning, especially in the south of the country.