1. Health Economics and Decision Science, School of Health and Related Research, University of Sheffield, Regent Court, 30 Regent Street, Sheffield, S1 4DA, UK
2. School of Health Sciences and Social Work, University of Portsmouth, James Watson Building (West) 2 King Richard 1st Road, Portsmouth, Hampshire PO1 2FR, UK
3. St George's Building, 141 High Street, Portsmouth, Hants PO1 2HY, UK