A Brit-com coming-of-age tale based in large part on autobiography and in small part on the oddball '70s classic "Harold and Maude," Jeremy Brock's "Driving Lessons" offers, among other things, the opportunity for Julie Walters to dive head first into a pool of raging eccentricity.

As Evie, a retired thespian who says whatever's on her mind, be it sane or salacious, Walters brings charismatic lunacy to this modest little film.

Rupert Grint, Ron Weasley of the "Harry Potters," is Ben, a painfully shy 17-year-old who lives in an oppressive, rigid household dominated by his religious mother (Laura Linney, with an English accent). Ben manages to escape the madness — by jumping into another kind of madness altogether.

On summer break from school, Ben goes to work for, and then on a life-changing car trip to Edinburgh, Scotland, with, the kooky Dame Evie (whose dameship, or damehood, or whatever you call it, may not be the real thing).

Not everything works in "Driving Lessons." But Grint's quietness at the center of things — and his character's palpable adolescent pain — holds it all together, even when Walters starts going overboard.