Thanks, that was super helpful!
It seems I got it the way around - it’s the Cine camera not being provided any budget, therefore, as it goes further away from the main one, it drops the quality. Added to the list 
Not sure about any quick workarounds, however. One thing that I can think of would be to position the main camera so that it’s looking down on the whole site (to avoid culling), drop the point cloud actor’s MinScreenSpace to 0 (under Performance), and up the point budget to something very high - like 10M+.