The government had a serious censorship regime, which regularly banned controversial books, newspaper reportage, and other media of both domestic and international origin. Conversely, yes, there are many many examples of authors and journalists subverting the censorship regime. During the 1980s, the Weekly Mail famously used to publish articles with visible redactions, indicating where illegal material had been struck out. Individuals caught distributing, or even just possessing, censored material could be imprisoned or "banned" (subjected to a status approximating house arrest).

For a more complete account, I recommend starting with Peter McDonald, The Literature Police (Oxford, 2010). Although McDonald focuses on the censorship of literary fiction, there is a thorough overview of the censorship regime itself in one of the first chapters.