Alsteomarias are just about the best herbaceous plants that can be grown in a British garden. The range of colour is everything but blue.
Only downside with some Alsteomarias is that many are weak of stem and prone to fall over. Try different varieties and grow those that suit your garden.
When the first flush of flowers die, just grip the stems and pull them up. A second flush will soon follow. They'll carry on flowering until the frost
To expand, just transplant a spadeful of root and water in. The foliage will die off, but quickly shoot up again. They're not fussy but do like a reasonable depth of soil.