There is a terrific warmth and emotional generosity to this romantic comedy-drama from the Welsh film-maker Janis Pugh, and if the storytelling in the end hits some familiar C-major chords, it’s not before a lot of inventive entertainment with quasi-musical sequences showing people singing along to the radio or the stereo morphing into full-on fantasy. I can imagine this being a stage musical crowdpleaser with serious ker-ching potential, packing the audiences in like something by Tim Firth or Willy Russell.

Louise Brealey and Annabel Scholey give seductive lead performances. Brealey plays Helen, a gentle soul living in a small town on the Welsh border with Merseyside, working at a local chicken factory. Her personal life is a deeply unhappy mess: her bullying and emotionally damaged husband has brought his girlfriend and their new baby (called Jacob-Rees) to live with them, and it’s furthermore Helen’s job to look after his ailing mother Gwen (Sorcha Cusack), who is the only person who has ever really cared for Helen.

But Helen’s life is utterly upended when an old contemporary comes back: Joanne (Scholey), who got out of that stifling town with all its macho, small-minded nastiness 20 years ago and has only returned because her abusive dad has died. Ever since girlhood, Helen and Joanne have been secretly in love, unable to admit their feelings to others or themselves. Can they now?

There are some sensational scenes here that involve simply singing along to emotional ballads: Helen loses herself in Neil Diamond’s I Am … I Said and Joanne sings along to Janis Ian’s From Me to You in her old childhood bedroom, in its entirety, cycling through moods of anger and triumph, getting emotionally wrung out in a way that only Ian’s music can cause.

• Chuck Chuck Baby is in UK cinemas from 19 July.