It sounds like Warrants in the RN are handled differently than Warrants in the USN, where they do pretty much the exact same jobs as O 1-3's. But that all said, American E 8-9 generally also occupy leadership positions, generally where an O 1-2 wouldn't be capable because of breadth of knowledge required, and an O 3 would be probably too high grade for the position.
Warrant Officer-2 and Warrant Officer-1 in the British Forces (RN, RM, RAF, British Army) stand above the Ordinary Ranks and NCOs, but are not commissioned, and are generally referred to by their appointments, e.g. "Regimental Sergeant Major", "Company Sergeant Major", "Regimental Quartermaster Sergeant", "Executive Warrant Officer", "Command Warrant Officer", "Master Aircrew", etc.
For a list of example appointments, see: https://en.wikipedia.org/wiki/Warrant_officer_(United_Kingdom)