Smartthings echo and lighting (UK)

Any lights that you can control from SmartThings can therefore be controlled by Echo because there is echo/smartthings integration.

There are very few switches available in the UK that work with SmartThings unless you have a three wire set up (including neutral). See the UK lighting FAQ for various options. But again, once you can control it from SmartThings you can control it from Echo for on/off/dim. Depending on the exact device you might not get the ability to change Colors through echo unless you set up some more complicated code.

The easiest option would be to get the Hue bridge and its bulbs as there is a direct Hue/echo integration as well which gives you a backup option in case SmartThings is not working. The Hue white only bulbs work well and are considerably less expensive than the RGBW models. But there are other brand options which are in the same range as the Hue Whites, although they may require a more complex set up.