After some help. Now, I'm no expert, but I've done plenty of bike maintenance, including rear hub/freehub disassembly/reassembly.
I picked up a second hand set of Shamal Ultras a few months. Hardly any wear to brake track, span smoothly etc. Couple of weeks ago I had some instances of where the pawls go 'bang', when they don't quite bite first time. Opened up the freehub to find a broken spring.
At the same time, I took the axle out to clean everything up. Put it all back together, and now I have a very annoying bit of play. Not the sort of play where you can feel it knocking at the rim and just tighten down the adjustable cone, but between the hub and freehub. There's no knocking, but if you pull and push hard enough at the rim you can create the play I mention. Tightening the cone down as far as I can makes no difference, other than a rough running wheel.
I even removed the whole axle/bearings/freehub from an older Zonda that had no play in the wheel at all, and get exactly the same result. So the issue must be something in the hub. Could it be a worn out cup?
The real annoying thing is I'm not certain whether I had this play before I took it apart. If you gently waggle the rim you get no play whatsoever.
Thanks in advance for any input!