I have entered The Bathride 80 mile sportive next July 5th. This is my first sportive and as such I must wear a helmet. I do not wear a helmet on the 6 days of the week I cycle at present but I understand from a H & S point of view that it is a requirement of all race/sportive organisers. So I plan to buy one to wear only for the sportive and any other sportives I shall do in the future. Therefore I only want the cheapest helmet I can buy (presumably wait for a Lidl/Aldi sale) and my question is are these up to the job? or do I need to buy something expensive that I only plan to wear when requested?