We took out some dead plants at the top (victims of copious dog pee judging by the smell - dog owners please don't let your pets pee on the plants!) and replaced them with Puyas. Or Dyckias. Can't tell the difference anymore, but they are spiky and hopefully will resist being killed by dogs.
We also moved about a dozen Nasaella tenuissima (Feather Grass), some Stachys byzantina (Lambs Ears) and some Euphorbia characias around to better groupings, and weeded a lot too.