You are not allowed to work under the conditions of having a visit visa. Even if someone offered you a job, it's still illegal.
You must also be able to show that, during your visit, you do not intend to:
- live in the UK for extended periods through frequent or successive visits;
- take paid or unpaid employment, produce goods or provide services, including the selling of goods or services directly to members of the public;
- do a course of study, as long as this study is not the main reason for your visit;
- marry or register a civil partnership, or give notice of marriage or civil partnership;
- carry out the activities of a business visitor, a sports visitor or an entertainer visitor; or
- receive private medical treatment.
http://www.ukba.homeoffice.gov.uk/visas-immigration/visiting/general/requirements/