I saw it around 20 years ago on TV. I think it was fairly new at the time. thought the star was Niamh Cusak but I can't find it on any of her filmographies. Anyway the star was someone like her — very softly-spoken and sort of "meek".
It's set in England and starts with her husband (and father of their 2 children) going off to war (I think it was WW2). While he's away she becomes very independent, even down to fixing the car's engine when it breaks down on the road!
Of course there is trouble when her husband comes back and doesn't like the changes... she ends up ditching him.
The only thing I remember specifically is her and the children singing a song in the car with the lyrics "there's sand in the gas"... and this recurred a few times in the film.
Please tell me if you know what this might be… It's been driving me mad for months!