[1] UCL, Dept Primary Care & Populat Sci, Primary Care Nursing Res Unit, London, England
[2] Univ Hertfordshire, Ctr Res Primary & Community Care, Hatfield AL10 9AB, Herts, England
[3] Kings Coll London, Florence Nightingale Sch Nursing & Midwifery, London WC2R 2LS, England
[4] Middlesex Univ, Burroughs, Hendon, England
[5] Middlesex Univ, Sch Hlth & Social Sci, London N17 8HR, England