As of this writing (2019) The Fibaro Smoke Sensor is the only one with an official SmartThings integration. It’s a good zwave device and popular in the U.K. (Note that there is no US version.)
https://www.smartthings.com/gb/products/fibaro-smoke-sensor
There are several other zwave smoke sensors made for the U.K., including Heiman, Popp, Vision, and Zwave.me , but I’ve only seen integrations for the Heiman, and I don’t know how well they work.
For something as important as fire safety, I’d stick with official integrations. Or get a good one like Nest and don’t integrate it with ST for any essential functions. JMO