Looking at the plants which give the best effect for the least effort I see that this border is very nearly perfect in that regard..(although past its best in this shot).
Geranium Rozanne (sometimes called Roxanne) is a star plant, and one of the longest flowering hardy geraniums. All it requires is cutting back at the end of the season. The agapanthus are totally reliable and easy. I grew some of them from seed and have just been given a couple more good sized clumps (thank you Liz) which I will put into this bed. I will take out the viola cornuta alba as they do not flower much here, but will certainly keep the campanula lactiflora which looks wonderful earlier but has now been cut back. With a bit of tidying of the edges and a good mulch of composted bark this really is a low maintenance part of the garden.
I have a lot of new plants of myosotis - forget-me-nots, grown from seed this year which I will put in here and perhaps some Bleu Aimable tulips? I am creating more work as I speak! I can't resist experimenting!