Thanks everyone, some lovely suggestions here. From these I've already picked a pulmonaria - silvery leaves and flowers that go from pink to blue will fit in wonderfully and I have the perfect spot for it.
And thanks for the reminder about lavender and rosemary, both of which have done very well here before.
I already have a spot earmarked for a ceanothus. I had a lovely one with soft, slightly lavenderish, pale-blue flowers, that climbed beautifully up the wall of the house. My ex-husband mistook it for a bit of the hedge (lonicera nitida) that had gone walkabout, and chopped it down (I cried). I'd like the same variety, but can't recall what it was called, so that will take a bit of research.
I dug out loads of white Japanese anemones last year, they grow like weeds here - you can't give them away! I will let a few that come up remain though, and maybe get a pink one.
I've chosen my hydrangea (a pretty blue lacecap called Bluebird) and where it will go, which will not only meet its needs but hide the compost bin, too. I think the pulmonaria will look great planted close by.
I don't think camellias would tolerate my chalky soil. I'm on the south downs, so very chalky, and you never see camellias in gardens. Five miles up the road, where the greensand of the Sussex Weald starts, they do brilliantly. That's one of my yardsticks - if something does well there, it will only do well here if it's incredibly versatile. Also to avoid things with japonica, siniensis or Himalayense in the name, as generally they don't seem to like alkalinity.
Then I have to think about the beds in the front, which are going to be completely different - hot colours, reds, yellows and oranges, broken up with white. The beds are in an L-shape, about 1m x 4m, and 5m x 3m, narrowing to about 1.5m where the bay window sticks out. It faces south-east, so is shady from mid-afternoon. There is a bay tree at the far end of the 1 x 4 bed, which I intend to prune into a decent shape. It's there by accident, it seeded itself, but the birds love it and I quite like its dramatic darkness.
I have a much clearer idea about that: rudbeckia, dahlias, kniphofia, helianthus, salvias, geums, dicentra alba, helianthemums and (if I can ever find plants for sale) wallflowers, because I love the scent; daffs, narcissus and really bright tulips will be planted in the autumn, ready to flower next spring.
As soon as The Archers is over, I'm off to the tip with yesterday's barrowloads of weeds, and then to the garden centre.
Thanks again. I think I'll take some photos, so I have tangible evidence of progress.