Sorry to be a pain, but do we have a schedule for the day? The limited running time means we need to be ready to go from the start.
No doubt it will be suitable, but better to try a helmet on before you buy. The fit varies surprisingly from one make to another, and it does need to fit properly. I always buy Bell helmets because they fit my head better than, say, Arai, although each are equally good helmets. Try to find a stockist in your area. I buy all my stuff from MSar in South London, even though I have to travel down from Bedford. Malcolm, who runs it, is extremely helpful. Check out their website for what they stock. Merlin, at Castle Combe circuit, are also worth checking.