I looked up online to see what info was out there, and read a lot about sinus headaches, but this didn't feel like that. It was a headache at the top and back of my head. But I tried adjusting the humidity and temperature of the hose, just in case, but it didn't really help.
Turns out my scalp must be really sensitive! I now wear a thick woolly hat under the straps - not had a headache since, so thought I'd pass that on in case it helps someone else
