The main character is a foul-mouthed impulsive hard-drinking ex-con neglectful mother of two with delusions of making it big in Nashville. She somehow is also a sympathetic character, and is beautifully played by Jessie Buckley. You might need subtitles occasionally to catch the full Glaswegian abuse and humour she manages to spout out. Other standouts are her two little children - remarkable performances by both - and a pretty impressive bit of character acting by Julie Walters as her despairing mum - complete with what sounded a decent accent, if a Sassenach can judge that.
As for the music and the plot.... it does the job but for me only occasionally hit the real emotional spot.