First off, the person complaining about "thick Glasgow accents" has obviously never hear a Glaswegian speak in "their native tongue" as the actors in this were speaking "drama school Scottish" with no accent of any kind, if they did speak Glaswegian of course very few outside of Scotland would understand much of what was being said, not a good thing for a film of course.
The poor living conditions were not an exaggeration of any kind as conditions then, and for many years later, were really that bad, several documentaries are available on youtube to watch.
An extremely gritty kitchen sink drama featuring a few actors who would go on to bigger and better things, one of them played Little John in the 1950s TV series Robin Hood.