Similar to the schemes provided for replacement windows and electrical works, you can avoid having to submit a Building Regulation application for certain elements of work if you employ a 'Competent Person Scheme Member' to undertake such works.
Certain members of Government approved trade bodies are allowed to carryout works - they still have to notify the Local Authority, but this is done by their Trade association.
See the Competent Persons leaflet (157KB) 
for further information.