I just typed a whole response and it's disappeared...how annoying.
I'm gonna just test that this one appears before retyping the original response...

Oh okay, that went through. My favourite shrub is Cotinus coggrygia Royal Purple, but I don't have one because there isn't room, its a large shrub.

For low maintenance, choose your shrubs according to height and spread and soil/light requirements. I usually aim for a mix of two thirds evergreen (if possible, it isn't always) and a third deciduous. I don't bother to take into account flowers, they're the last thing on the list when I make choices - I tend to go more by overall appearance, leaf shape, size and colour because that way, the garden always looks interesting, even when nothing is in flower. That said, I would try hard not to plant 3 different white flowering shrubs in a row...but will try to choose something with dark (black or purple or brown), yellow, grey, red, variegated, dark green and light green mixes of leaf colour. Also use the designer's trick if there's a lot of space to fill - use 3 or 5 of the same small or medium sized shrubs together. Add some well behaved ground cover plants (preferably flowering but well behaved is more important, which definitely rules out Vinca!).

Some of my favourites are Escallonia, Euonymous fortunei (Emerald and/or Silver), Hebe and Pieris japonica. Clay soil here too!

If you want dead easy and long flowering how about Potentilla fruticosa? latish coming into leaf and not pretty in the winter but flower their socks off all summer. Shades include white, yellows, orange and red (latter best in light shade)

Agree re the Euonymus, both silver and gold ones.(bright all year round and shade tolerant)

(If you go with Bamboo's Cotinus try to plant it so that the sun shines through the leaves rather than on to them - looks wonderful.)

A Philadelphus if there's room, for the scent.(if you are wiling to prune it after flowering)

Again if there's room a red stemmed dogwood, planted where the bare stems catch morning and/or evening sunlight.(though it needs taking back almost to the ground every spring)

Well, Bamboo, Shirley and Stera! Thank you all for these ideas. Unfortunately I won't have room for groups of several the same, Bamboo but I've taken on board the idea of a mix of shapes, shades and textures, and two thirds evergreen. Is it a good idea to include small conifers in such a border or not?
Stera, thanks for the tip about where to position a cotinus. It's made me realize that the one I have at the front of the house is entirely in the wrong position! I'll try a potentilla-have never grown one and both you and Shirley mention Euonymous as reliable. I actually rescued 2 this spring from Wilco's. They are both bright, one silver lined and one in shades of orange but each was labelled simply,'shrub'! They are in pots at the moment. Shall I put them in full sun or partial shade? Oooh! I'm going to have such fun using my cow moneybox full of £2 pieces, which is my garden fund! Thank you very much.

You could also add a grass, say Miscanthus, to the sunny border to give a different and lighter shape.

The Euonymus are tolerant of sun or shade Pennyfarthing. Worth their weight in gold in my book... I have 5 of them, plus a couple I'm having a go at making into low standards! though they take a while to get going...)

No reason why you can't include conifers in a mixed border - just make sure you don't choose a giant one by mistake - the sizes quoted on the labels often refer to the height within 5 or 10 years rather than at maturity.

skimmia for me. evergreen fragrent flowers pretty berries [if you have a female or a self fertile variety] and pretty flower buds from autumn through to spring.

Right, skimmia, escallonia and miscanthus added to the list! Thanks all. I won't have room for all but now I've got a good list to choose from.

Okay, here's a few more to consider - Sarcococca for shadier places (preferably somewhere you walk past early in the year to catch the fragrance from the flowers), Brachyglottis for evergreen grey foliage (sun or shade) Osmanthus heterophyllus 'Goshiki' for its great coloration (slow growing), and a couple of deciduous ones - Spirea Goldflame and Berberis atropurpurea nana or Berberis 'Bagatelle'... or even B. 'Admiration' a little larger in spread. All low maintenance favourites. Also Hebe youngii, unless your garden is really, really cold in winter, and Helianthemums for evergreen ground cover and spring flowers (in full sun).

Crumbs! Thanks Bamboo! Will look all these up and check the garden centres.