You know the 'rules' - personal choice...
Here (may be) some stats -
"
There are confusing statistics surrounding the debate over the use of bicycle helmets for both adults and children. Some research points to helmets encouraging car drivers to give cyclists less space in traffic. Up to a third of children in another study said wearing a helmet would put them off cycling in the first place - bad news for parents concerned about childhood obesity. GP Margaret McCartney uses her own risk analysis to work out how to keep herself safe and fit."
http://www.bbc.co.uk/programmes/b01f5mn6
On shortly + iPlayer