I bought a Harry Hall Legend Plus in summer this year as I was really suffering with the heat in my HS1. I love it, nice comfy fit and good ventilation with a nice lining.
Ive just bought a casco mistrall helmet (£75 using H&H christmas deal), it has the best ventilation out of any hat I've had! When hacking the other day in breezy weather I could actually feel the air circulating round my hair under helmet when walking into the wind. Very lightweight too, I'm pretty pleased with it . I also have a gatehouse conquest that has good ventilation, but casco is better.