I finally got this sorted (I did buy a new ‘main’ bike in the meantime, with a lefty, so the issue became a little less priority) using the hope adapters (£20 – but as above this could be got cheaper) and a specialized 9mm bolt thru axle (£10).
The specialized axle was new from the Specialized concept store Brum, I phoned up and asked for a replacement one for a stout hub, they had to order it in, but other than being passed to a mechanic to confirm what I wanted, it was no bother at all (I believe they were going to order some spares in too).
I can throughly recommend it, but can’t prove it hugely better (I hadn’t actually ridden this bike for over 2 months), but perception wise it feels ace, with the bike seemingly tracking better.
This perception is throughly endorsed by the fact that when you pull the end caps off your Pro II hub there is nothing supporting the skewer inside the hub it it only supported by the end caps! I hadn’t expected this, I was expecting an axle like the rear hubs (and was wondering what I’d need to pull out to make the 9mm axle work).
So having a bigger 9mm axle runnning through the two new endcaps was a better mental image before you even start riding.
Can’t say I think the specialized axle is a greatest piece of kit but when the alternative is a £50 DT axle, I’ll stick with it for now.
It may be worth seeing what the Ritchey 9mm bolt thru axle is like, but as I found the specialized one so easily i didn’t chase that up.