Total newbie help required (UK)

Zwave should be compatible with SmartThings, although some older “scene controllers” may not work as expected. And because zwave frequency varies by region, you have to make sure you’re ordering one that has the correct frequency for your hub.

Zigbee is a whole different story. There are many zigbee devices that do not work with SmartThings. See:

And I second the recommendation for Vesternet. Excellent technical support, good technical information on the website, good selection. Not everything there will work with SmartThings, so always check the forums before ordering, but it’s definitely one of the dealers to consider:

There are some more shop options listed in the following thread: