Are you allowed to work in The United Kingdom? Work Permits explained.
EU, EEA and Swiss Nationals do not need a work permit or visa to work in the UK. If you are not from the UK or EEA or Switzerland you may need a visa to visit the UK, you can apply for a visa at a British Overseas Mission in your own country, having a visa does not always mean that you can work in the UK, if it says ‘prohibited’ on the visa you will need a work permit to work here.
The UK no longer issues work permits to non-EU/EEA or Swiss citizens but you can apply to work here permanently if you are a highly skilled worker, applications are considered on a points system. More information about the points system and how to apply are available on the UK Border Agency website - http://www.ukba.homeoffice.gov.uk/visas-immigration/working/tier2/
If you are a temporary worker the above application and points based system does not apply – details of the requirements are here - http://www.ukba.homeoffice.gov.uk/visas-immigration/working/tier5/
If you are a student you may have the right to work here whilst you are studying. If you have a student visa you can work here outside of term-time, and up to 20 hours a week (outside of coursework or internships). You cannot however provide services as a professional sportsperson or entertainer, take a full-time position, run a business or work for yourself (self-employed) More details can be found here - http://www.ukba.homeoffice.gov.uk/visas-immigration/studying/