Yeah the only real difference with a £70 helmet over a £20 helmet is that they have a lot less space actually covered by helmet so the helmet needs to be stronger to give the same strength as the cheap one. I've got a specialized one that cost me about £20-£25 and it's great. One thing I heard once was "if you've got a £20 head. Buy a £20 helmet". I don't really agree with that for cycling helmets. It's more for motorbike helmets.
Yeah the only real difference with a £70 helmet over a £20 helmet is that they have a lot less space actually covered by helmet so the helmet needs to be stronger to give the same strength as the cheap one. I've got a specialized one that cost me about £20-£25 and it's great. One thing I heard once was "if you've got a £20 head. Buy a £20 helmet". I don't really agree with that for cycling helmets. It's more for motorbike helmets.