Cossey started transitioning whilst serving in the Corps of Royal Engineers after befriending a post-operative trans woman who was serving as the 9 Sqn RE SSM. By 19, Cossey was receiving hormone therapy, serving full-time in a female gender role and had begun to split her time between working as a Shipwright and starting a part-time career as a showgirl at a London nightclub. Despite initial shock, the Corps of Royal Engineers were eventually supportive. Following breast augmentation surgery, Cossey worked as a showgirl in Paris and as a topless Dancer in Rome to save up for sex reassignment surgery (SRS). After years of hormonal and psychological treatment, and legally changing her name, Cossey had her final surgery on 31 December 1974 at Charing Cross Hospital, London.

In 1978, Tula won a part on the game show 3-2-1. A tabloid Journalist then contacted her, revealing he had discovered she was transgender, and planned to write about it. Other journalists researched her past, attempting to interview her family members. Cossey dropped out of the show, convincing the producers to release her from her contract. After this incident, Tula maintained a lower profile, accepting only smaller assignments.

Tula was cast as an extra in the 1981 James Bond film For Your Eyes Only. Shortly after the film's release, the tabloid News of the World came out with a front-page headline that read "James Bond Girl Was a Boy." By her own accounts, Tula was so upset she contemplated suicide. However, she continued her modelling career. Tula responded by releasing I Am a Woman, her first autobiography.

In 1985, Tula appeared extensively in the video for The Power Station's "Some Like It Hot". After breaking up with Lasinio, Tula met Elias Fattal, a businessman, who was unaware of her history until he proposed marriage on St Valentine's Day 1988. When she told him, rather than rejecting her, he merely asked if she would convert to Judaism. She agreed. They were married on 21 May 1989, just weeks after the European Court of Human Rights decided legally to recognise Tula as a woman. They returned from their honeymoon to find that the News of the World had published a story on their wedding.

On 27 September 1990, the European Court overturned its decision on a British government appeal. Later, the Gender Recognition Act 2004 was passed, giving transgender people in the United Kingdom means to change their legal sex. Tula returned to modelling, which she had given up four years earlier.

In 1991, Tula released My Story, her second autobiography. In it she gave details of her transition and her unsuccessful battle with the European Court. She was featured in the September 1991 issue of Playboy, in a pictorial, "The Transformation of Tula", as an acknowledged transgender person.

Tula married Canadian David Finch in 1992. They live together in Kennesaw near Atlanta, Georgia, US.