And once you've checked billyscrashhelmets, this is a useful next stop.
https://sharp.dft.gov.uk/
Dave's advice is good. It's best to try various helmets on. I'm using a Scorpion Exo and it's a good fit for me. Shark and AGV are OK for my head but HJC is a complete no no. And it was Arai good and Shoei bad or vice versa, can't remember.
Plenty of places to try in North Yorkshire. Infinity York have a good range, a couple other places in York too. Teasedales in Thirsk and more options in Darlington/Teesside.