In that case, it’s much easier.
If you want to do this with SmartThings, you will need the smartthings UK model hub for any project. At present it is only available from Currys or the Samsung UK site.
As far as light switches, most standard Z wave switches will work with SmartThings, although some “scene controllers” will need custom code.
Vesternet is a reliable online retailer with excellent technical support and a good selection. You can browse their Z wave devices to see what looks good to you, and then ask about specific models in the forum. They do offer a number of other technologies like enocean, but only the zWave will work directly with SmartThings. Since you do have a neutral at the switchbox, you should be able to use most of the Zwave light switches shown.
Again, if you go with SmartThings you would be able to use either Z wave or zigbee home automation (ZHA 1.2) motion sensors. One of the advantages of SmartThings is that you are not limited to the devices of its own brand as long as the device is certified for either Zwave or ZHA 1.2, although in some cases custom code may be required to take advantage of some features of a device.
If you choose to go with the Devolo hub or one of the other smartthings competitors, some of those are Zwave only, so it’s important to decide on the hub before you start buying devices or you might end up with incompatibilities.
Protocols supported by SmartThings:
And the official “works with SmartThings” list for the UK. You will notice that there are no light switches on it at all. ( there are several in wall modules that are used to control lighting.) But most of the zwave switches that vesternet sells will work. However, you should be aware that SmartThings support may not be able to help you with a device that is not on the official list, so that can also affect device choice.