Posted: 13/04/2017 at 22:59
Hi Gavin - I think you are over complicating your soil conditions, roses aren't over fussy with PH but for extremes, best to work with the soil you've got than trying to change it. The clay soil is no problem for roses either if anything they love it, roses are very greedy plants and clay locks up nutrients.
I spray aphids with fairy liquid does the after job after one or two applications. Or I squash them if there a lot.
Other than remove fallen leaves in autumn and prune out very affected stems I dont know what else you can do organically with the rust problem. The high potash feed should help but it might be something your going to have to persevere with.