Footnotes

• Contributors The project was conceived by TW, CS and AEB. AEB, TW and CS prepared the questionnaire. Data were collected by AEB and LM. Data were analysed by AEB and LM. Write-up and critical analysis were done by AEB, LM, TW and CS. All authors read and approved the final manuscript.

• Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

• Competing interests None declared.

• Provenance and peer review Not commissioned; internally peer reviewed.