I've replaced both headset bearings, added and removed shims, done up and undone cable guides and flushed them with silicone spray, sprayed all the linkages with lube... It's still clicking.
Next thing is to try removing and refitting the headset cups in case it's dirt somehow in between them and headtube.
Is the whole headset Hope or just the bearings? Some companies can have funny dimensions for the cups which can mean another brand's bearings sit on the flats rather than the chamfer.
It's a Hope headset, now with replacement bearings but they're the correct spec. The click started with the original Hope bearings and hasn't gone away, so it's not that.
I've replaced both headset bearings, added and removed shims, done up and undone cable guides and flushed them with silicone spray, sprayed all the linkages with lube... It's still clicking.
Next thing is to try removing and refitting the headset cups in case it's dirt somehow in between them and headtube.