The UK domestic electrical industry falls under Part P legislation, commercial/industrial is different so in a nutshell you'd need to at least partly requalify then join a scheme in order to certify work unless you do so at a higher cost through building control. Have a look on the ELECSA / NAPIT / STROMA / NICEIC websites for more in depth info. http://www.elecsa.co.uk/Contractors/Part-P.aspx