Hi Jack - don't worry - Verb. bon is quite accomodating, and should be no bother in your garden
Very little needs done to them, so you can simply remove the flowerheads when they finish. This can look a bit odd, so normally you take the whole stem that carries the flower, back down to the next 'joint' on the stem. It's a good idea to leave them like that over winter as it protects the plant if you get very cold spells, and then in late winter/early spring, you can tidy the plant up by removing any stems that look a bit rough or are dead. Again, just cut them off back to a joint on the stem. You can actually cut them right back at that point if you want, as they'll produce new growth from there.
Having said that - many people leave the flowerheads on and let them seed around, because they can sometimes die if the garden soil is very wet and heavy, or you get a long spell of sub zero temps. As you're very urban, and down south - that probably won't happen!
You could experiment and try pruning a few in different ways too. It's often a good way to determine what suits your own conditions. Leaving some to seed can be good if you want to increase the number of plants, but it depends on the look you want to achieve, as they'll grow where the site suits rather than the place you want them. You can also take cuttigns from them by using the bits you cut back in spring, but if that interests you, it's probably better to wait till then and come back and ask - we don't want to confuse you!
Hope that's a little help for now.