Maybe I've got it wrong here, someone please correct me if I have.
Don't ALL cycling helmets, irrespective of price point, given the job they may have to do, go through stringent testing and have to have some kind of kite mark stating that they are up to said job if called upon?
If so, then a £10 helmet should offer the exact same level of safety factor as a £300 helmet???
If that is the case then choice of helmet is purely for aesthetics, and not safety. The safety aspect is a given, or should be.