Suggest you speak with Inglesport and/or Starless River and look for at alloy-body headtorches on elastic strap.
I have used Fenix HL55 for a few years, which has been great. Robust, waterproof, and the 18650 batteries to easy to source/charge/replace. Can be used on or off helmet. Now superseded by HL60R, which is rechargeable.
The smaller HL50 (now superseded by HM50R) would be very adequate for starting out and is more handy for camping/running/backup.
It is not necessary to spend as much as ?100
I have been searching around for the best,cheapest, truly waterproof headtorch with not a lot of success. But that HL60R looks really good at a good price too. 950 lumens is pretty high. So thank you for the advice and review.