Writer-director Craig Roberts has created a thoughtful, valuable, humane drama about mental illness. The setting is a British suburbia around the 1980s – pay phones, dodgy clothes, terrible cars – and Sally Hawkins plays Jane, a young woman experiencing depression and schizophrenia following the trauma of being stood up at the altar. Morfydd Clark plays Jane in flashback as a young woman. Jane has mood swings, hears voices and has a bullying mum (Penelope Wilton) and sister (Billie Piper). Another, more caring sister (Alice Lowe) is pretty much her only friend and ally. Her life appears to turn around when she meets another patient, Mike (David Thewlis), but this whirlwind affair alarms her family and brings problems of its own.

Roberts and Hawkins intriguingly take this movie, and us, on a kind of tonal journey: it begins on a note of standard-issue satirical black comedy; then morphs into suppressed horror as the film guides us inside Jane’s lonely and bewildered world, disturbingly repeating a certain image and phrase; and then it moves into something more tender, and more moving, as Jane comes to terms with her condition and builds a new relationship with her family.

Hawkins delivers a very detailed and mannered performance in her distinctive style. At first this fluttery, jittery persona can be a lot to take, and if all the movie had to offer was a sustained exercise in quirky irony it would not have worked. Instead, it finds its way through the archness and flippancy, towards something richer. As in Mike Leigh’s Happy-Go-Lucky, the film allows you a sympathetic and emotional connection with the vulnerabilities of Hawkins’s character. This is substantial and rewarding.

• In cinemas and on digital platforms from 2 October.