Obedient plant!!! Be careful. I was given 6 stalks of these 2 years ago and now I believe I have 600!!! And that is after thinning every year!!! Very pretty...but VERY invasive.

I am totally unfamiliar with what you can or can't grow in 'SW UK 8/9', or what local names plants are given. Here, Sub-tropical New South Wales, Australia, the name 'summer bedding' is certainly not used. I also checked with my English neighbours and they'd never heard the term. Many colourful varieties of coleus are grown here - nurseries are full of them - all year round. You might find that informative, flora_UK!

It does go to show how photographs don't always tell you what you need to know. Googling most plants just gets you a zillion close up images of the flower, especially if it's something most known for its flowers. But that doesn't help you ID the plant without flowers. It also doesn't help you understand the overall form of the plant. If it's a garden plant you're looking at and you want to decide whether to grow it, you want to know what its shape is and how it would fit into the space in your garden. Even a pretty good photo of the whole plant probably doesn't distinctly show all its parts. We better not forget how to hand-draw plants because that's often the best way to get a useful image.

There is a perennial ageratum, commonly called mist flower, scientific name Conoclinium coelestinum (no, I didn't remember that, and won't try to pronounce it ;-). It is native to southeastern U.S. and is reportedly winter hardy to zone 5.