If I looked for similar newer hubs, 10mm axle, 9 x 0.25" balls, I think I should be able to make it work
You probably can, although Shimano have a habit of making the lock nuts/spacers/washers different thicknesses for every damn hub, so you can end up having to dial in the spacing with whatever is in your parts bin to get it to exactly 135mm OLN.
You're effectively getting a fresh freehub rotor for £12, so it seems like a no-brainer to forgo a few beers and have all the bearings in your hub renewed while you've got the axle out anyway.
You probably can, although Shimano have a habit of making the lock nuts/spacers/washers different thicknesses for every damn hub, so you can end up having to dial in the spacing with whatever is in your parts bin to get it to exactly 135mm OLN.
You're effectively getting a fresh freehub rotor for £12, so it seems like a no-brainer to forgo a few beers and have all the bearings in your hub renewed while you've got the axle out anyway.