LONDONAvalon Management Group has bought rival talent agency Artists Rights Group from All3Media for an undisclosed amount, it was announced Friday. ARG, founded in 2001, was bought by All3Media in March 2006 and represents a variety of actors and presenters, including “Harry Potter” stars Daniel Radcliffe and Imelda Staunton. The agency will operate independently under the Avalon umbrella. The Avalon Group was founded in 1989 and comprises nine companies, including Avalon Management and Avalon Television. The group has offices in London, Edinburgh and Southampton in Blighty, as well as in L.A. and Gotham. Avalon Management clients include Chris Addison (“In the Loop”), Greg Davies (“The Inbetweeners Movie”) and Kristen Schaal (“The Daily Show with Jon Stewart”).