Posted: 04/09/2014 at 08:52
Sounds like a lovely selection of flowers. Not sure if delphiniums will do what you want - most are not annuals and won't be in flower by the summer. But if you can find some elsewhere, perhaps in a friend's garden, they should be flowering around the right time. Many are too big but you.might find some new, small spikes.
Verbena Bonariensis would look good but I don't think you can grow it from seed in the time. But this and other perennials can be bought now in pots, and planted out as soon as you find space. Our local Morrisons had some perennials at £2, including Alchemilla Molllis.
Do keep back some seeds for next year, in case those you sow now don't survive the winter.