During the Second World War, Hilda attended Summerhill School in Suffolk, before leaving in her mid-teens and starting to live in Swiss Cottage, London.
She joined the Young Communist League, and then the London Youth Choir set up by university lecturer John Hasted.
She travelled with the choir to festivals in communist eastern Europe, and by the mid-1950s also sang and played guitar in coffee bars in central London, while working at Collet's book and record shop.
During the British skiffle boom of the mid to late 1950s, and later, Sims toured widely as a member of the City Ramblers, and recorded for the Storyville and Topic labels.
She later taught English as a foreign language in London and Spain, and established Lifespan, a residential community at Dunford Bridge on the South Yorkshire moors.