The emancipation of slaves in England preceded America by thirty years and freedom was won by legal court cases not bullets.
Somerset v Stewart (1772) is a famous case which established the precedence for the rights of slaves in England. The English Court of King's Bench, led by Lord Mansfield, decided that slavery was unsupported by the common law of England and Wales. His ruling:
The state of slavery is of such a nature that it is incapable of being introduced on any reasons, moral or political, but only by positive law, which preserves its force long after the reasons, occasions, and time itself from whence it was created, is erased from memory. It is so odious, that nothing can be suffered to support it, but positive law. Whatever inconveniences, therefore, may follow from the decision, I cannot say this case is allowed or approved by the law of England; and therefore the black must be discharged.
E. Neville William, The Eighteenth-Century Constitution: 1688-1815, pp: 387-388.
The Slavery Abolition Act 1833 was an act of Parliament which abolished slavery throughout the British Empire. A fund of $20 Million Pound Sterling was set up to compensate slave owners. Many of the highest society families were compensated for losing their slaves.
This act did exempt the territories in the possession of the East India Company, the Island of Ceylon, and the Island of Saint Helena. In 1843, the exceptions were eliminated.