"The words aren't really poetical, in the way that someone like Ewan MacColl with great awareness of language."
I don't think you could be more wrong about this Al - MacColl was one of the great advocates of the poetic power of the vernacular speech which went into the making of our folk songs and ballads

"I saw the new moon yestereen wi' the auld moon in its Arms" - a beautiful description of a haloed moon
Or this brilliant example of black folk humour
"O laith, laith (loath, loath) were our gude Scots lords
Tae wet their cork-heelt (heeled) shuin (shoes);
But lang or aw the play wis done
They wet their hats abuin. (above) "
"I once was fu' o' Gil Morrice as the hip is of the stone" - was there a more powerfully beautiful description of pregnancy than comparing it to a rose hip berry with its huge stone and its wafer thin layer of skin?
Even songs like Van Dieman's land with its simple description of a view from aboard a ship in the middle of the ocean, "all around us one black water and above us one blue sky"   
"It?s I would sleep in Jimmy's arms, though his grave was growing green ? magnificent!
"Sheath and Knife? " a brilliant sexual metaphor
This is vernacular poetry at its very finest.

MacColl's very best songs (in my opinion) were those lifted directly from vernacular speech; Freeborn Man came from hours of actuality recorded from Travellers (I have many of the original recordings, but you only have to listen to one Radio Ballad to see what I mean)
'Shoals of Herring' - straight from the words of Sam Larner and fellow East Anglian fisherman, Ronnie Balls - Sam Larner found the song so convincing he once said he'd been listening to it all his life though he couldn't remember ever hearing it sung by anybody
'Shellback' taken directly from the words of merchant seaman Ben Bright, who served under sail, jumped ship to join The Wobblies and was discovered working as an escapologist's assistant on London Bridge
'Tenant Farmer' based on an interview with Scottish border formers who had been evicted from their farms to make room for the Multinationals and Forestation.
'Freeborn Man' taken from the interviews with Minty Smith, Belle Stewart and Gordon Boswell.
This is why I believe the suggestion that our folk songs originated on the broadside presses to be utter nonsense - the city-based hacks would have to have been fully conversant with vernacular speech, folklore, social history and rural and maritime work practices to create such poetic gems

Having said that, I do believe that there is always a danger of these discussions taking flights of academic fantasy
Typical is Phillips Barry's notorious note to one of the most beautiful descriptions of a local drowning tragedy in the repertoire, Lake of Col Finn, where, by the use of metaphysical gibberish he turns the death of a young man into a mystical tale of water-sprites, magical islands and malignant seaweed.
There are some signs that this is beginning to happen here; this is simply a song of a young man or woman dying of the clap; everything else is charactarisation.
These songs are basically straightforward stories presented in the language of the day (wherever and whenever that "day" may be.

MacColl always insisted on comparing the language of our folk songs and ballads to that of Shakespeare - there's a great deal of evidence to support that
Shakespeare (simple son of a glove-maker) borrowed liberally from contemporary folklore and custom; why not vernacular language?
One of the things we were encouraged to do in the Critics Group was to analyse the songs and learn to use every aspect of their construction in our performances
Returning to those songs after decades of not having sung them, I am now realising the value of having adopted that practice, my songs work as well for me now as they did forty or fifty years ago, if not better
Jim Carroll