There are seven standard ways to apply for a work permit in the United Kingdom: the Business and Commercial Arrangements, the Training and Work Experience Arrangements, the Sports people and Entertainers Arrangements, Student Internships, GATS, Ancestry Visa and the Sectors Based Scheme.

Each of these involves its own application process, and generally requires a job offer from a UK employer. The UK has stopped accepting work permits in many other categories.
There is also a scheme for nationals of select countries to work in the UK as au pairs. This scheme is only for nationals of European Economic Area countries don't need a permit to au pair in the UK. The UK work permit system is currently being replaced by a new points-based immigration system.