Wee Little drummer says " Ewan wouldn't have given a tinkers todger if you thought it was about Blackpool or Bangkok - and that's why people all over the world respond to it." and I suppose you're dead right. Trouble is - Salford and sulphured can be very close in pronounciation if said quickly especially in various accents.
What causes a little confusion for me reading this thread ,is , I learned the song in the early 60's , from where I can't remember, and I always sang sulphured wind. It made sense after the steam train going past, though, I always appreciated that the song was about Salford. It further begs the question, why did so many people used to discuss which town the song was written about, if, it already contained the name Salford.,Curious. I don't think it did but I'm willing to recieve informed advice. No matter, On the subject of croft - it has a proper meaning in Scotland, but in the N.East where I live , we would use the word " common". A piece of inner-city scrub, waste or derelict land, on occasions used by Gypsies , Fairground shows, bonfires etc. and all the other dumping described by others earlier in this thread.
I suppose McColl was painting a picture of the grim reality of growing up in a dirty Northern town, much as L.S.Lowry did with a paint brush. We must remember that most Northern and many Midland towns and cities were /are heavy industrial towns especially up to the 1970's, and to varying degrees, were filthy places to live because of the use of coal, to power the vast industries. I was born in the late 40's, in a steel town and it was certainly a dirty old town.
A good comparison perhaps of the American and the British way of looking at this type of song - give Billy Joels " Allenstown " a listen. Yeh I know thsi is a Folk site, but .....

Cheers
Betsy