If the new part P allows installers who are not registered competent persons to appoint a registered third-party certifier to inspect, test and sign off on the work. Am I right in thinking that this would allow a DIY'er to arrange to do the work if they arrange for a registered third-party certifier?
Link to new part P http://www.planningportal.gov.uk/buildingregulations/approveddocuments/partp/approved#Download
Link to new part P http://www.planningportal.gov.uk/buildingregulations/approveddocuments/partp/approved#Download