[1] Department of Congenital Heart Disease, Bristol Heart Institute, University Hospitals Bristol NHS Foundation Trust, Upper Maudlin Street, Bristol
[2] Department of Psychology, Bournemouth University, Poole
[3] Health Economics, Musculoskeletal Research Unit, Southmead Hospital, University of Bristol, Bristol
[4] Research Design Service, Taunton and Somerset Hospital, Taunton and Somerset NHS Foundation Trust, Taunton
[5] Bristol Heart Institute, Upper Maudlin Street, Bristol
[6] Department Congenital Heart Disease, Bristol Royal Hospital for Children, Upper Maudlin Street, Bristol
[7] Plymouth Science Park, Plymouth University, School of Medicine and Dentistry, Plymouth
[8] Hammersmith Hospital, Du Cane Road, London
[9] Research Design Service, University Hospitals Bristol NHS Foundation Trust, Upper Maudlin Street, Bristol
[10] School of Social and Community Medicine, University of Bristol, 39 Whatley Road, Bristol