If I’m not mistaken, the FS20Z-1 requires mains-level input, in other words you need to tie it into 120v AC. Good for devices built into the wall, but wouldn’t work for battery powered devices. Since it also specifies 115v operation, I would also be concerned about use in the UK.
You’ve got two levels of difficulty here- First, you’re in the UK and most of us in the US are really unfamiliar with what’s available. Second, most battery operated devices are types of sensors, meaning that the information generally only flows from the sensor to the hub, not the other way.
I’ve done a hack to create a battery operated LED based on a CREE lightbulb Zigbee module. I doubt the same products would be available for you to use, but the concept may work if you can find a compatible board.
Other interesting links: