What are the architectural design practice limitations for a draughtperson in UK?

I would like to know the limitations for draughtpersons in UK especially in the architectural field.I know most draughtspersons design extensions and lofts and prepare CAD drawings but what is the limit to their practice and also if there are any ociations or societies for draughtspersons in UK.Im sure there is someone out there who can share some bit of information regarding this..............