For Imogen. I can only tell you which perennials I have grown in my tiny garden. Hopefully, others will tell of their experience too.
There is not the wide range of plants that one can grow in a more temperate garden, but there are still some beauties.
Aster x frikartii Monch. This is an absolute star in my garden. It starts flowering in May and continues into the winter. Mine still had some blooms on it, when I cut it back last week.
sept 2013 033 by
Daisyincrete, on Flickr
Lychnis coronaria. Seeds around, but is easy to pull out or transplant.
sandy6 021 by
Daisyincrete, on Flickr
Rhemannia elata. This spreads, in sun or shade, but is easy to control.
sandy6 037 by
Daisyincrete, on Flickr
Sedums, all of them I have tried, are happy.
sandy2 125 by
Daisyincrete, on Flickr
Zantedeschia aethiopica, Arctotis hybrids, Erysium Bowles Mauve, Verbena x hybrida, Dahlias and Tanacetum niveum Jackpot are all happy here.
sandy6 043 by
Daisyincrete, on Flickr
Echinacea purpurea.
sandy5 145 by
Daisyincrete, on Flickr
Limoniums. All of them.
027 by
Daisyincrete, on Flickr
Long flowering Alstroemerias. All of them that I have tried.
may 2013 097 by
Daisyincrete, on Flickr
may 2013 138 by
Daisyincrete, on Flickr
Nepeta Walkers Low. Seen above with the alstroemeria. This is another plant that flowers for most of the year.
may 2013 120 by
Daisyincrete, on Flickr
Valerian. Seeds like crazy.
may 2013 060 by
Daisyincrete, on Flickr
Geums. I only planted my first geum last year.The chiloense types are best for this climate. This is Mrs Bradshaw, still a young plant.
may 2013 043 by
Daisyincrete, on Flickr
Erigeron karvinskianus. This seeds like mad too, but is easy to pull out.
april-may 2013 060 by
Daisyincrete, on Flickr
Salvias. All of them.
021 by
Daisyincrete, on Flickr
Verbena bonariensis. Here with Nicotiana sylvestris. All the verbenas are happy here. I also have Verbena rigida which spreads a bit, but is easy to pull out.
Anemone hupenhensis. These don't start flowering here until October. They are truly autumn flowering.
Galliardias, and Gazanias, seem to be short lived, but flower for ever.
Pinks are also short lived, but easy from cuttings.
april-may 2013 020 by
Daisyincrete, on Flickr
Agastache Apricot Twist is good for cuttings too.
All Artemisias. This one is Powis Castle.
may 2013 119 by
Daisyincrete, on Flickr
Perovskia atriplicifolia flowers for ever and goes on for years.
032 by
Daisyincrete, on Flickr
Achilleas. I only have Cerise Queen so far. I haven't tried any others yet.
may 2013 152 by
Daisyincrete, on Flickr
Argyranthemums. All of them.
may 2013 076 by
Daisyincrete, on Flickr
There are lots more like Hemerocallis, Hellebores, Lavenders etc.
Perhaps others can tell you what perennials they grow.
Hope this helps.
Daisy