OK. First on the question of jurisdiction. The fine was imposed on Loveworld Limited, a British registered company, so the fact that Oyakhilomes is based in and broadcasting from Nigeria is irrelevant. It appears that most of his finance is raised in the UK via Loveworld.
Secondly, the fine was not imposed by 'the British Government'. The British government has no power to impose fines. It was imposed by OFCOM, the independent media standards regulator. OFCOM is not part of government. It has statutory duties derived from the Communications Act of 2003, and is accountable to Parliament, not government.
In the United States, an independent agency of the Federal government, like the Federal Deposit Insurance Corporation (FDIC), has the authority to impose fines on violators of banking regulations. The decisions of these agencies are subject to judicial review but if the decisions are upheld or the violator signs a consent order, the fines are enforceable by the courts and the agency has the authority to seize bank assets or individual assets, if the fine is imposed on a bank officer. The FDIC has basically the same enforcement powers as the Office of the Comptroller of the Currency, a branch of the Treasury Department which charters and regulates Federally chartered financial institutions. The FDIC regulates those State chartered banks that are not members of the Federal Reserve System.
If OFCOM has the ability to enforce its fines through the courts, including the power to seize assets, then that agency would be analogous to the FDIC.