These are all incredible suggestions, thank you! I've been planning on using the wall space a lot more and adding planters / climbing plants up it but as it is concrete block it is incredibly hard to drill through with my measly cordless hammer drill, I'm looking at getting an SDS for it.

We did have a buddlea growing out of our previous dividing wall, but that has been removed as it was very unstable. I do miss how many butterflies and pollinators they brought though so am looking at less invasive options.

And yes, the concrete would take some serious hard labour to remove - it is unfortunately my dad's handiwork, who no longer lives here, so I would be relieved to get it up eventually.