MK Astral is indeed an expensive system, really intended for commercial lighting installations like hotels or an entire apartment building. Not so much homes. I believe it does require a neutral wire at The switch.
It is a certified Z wave system, but it’s what’s called a “lighting scene controller system” and consequently uses some Z wave command sets which SmartThings does not support. In particular, it requires controller replication. So the devices probably wouldn’t work with SmartThings anyway.
TKB make some wall switches for use in the UK, but they also require neutral at the switch. They cost a lot less than the MK Astral but they’re still probably close to £40 per switch. They are sold for individual homes, and you could find them, but unless you’re doing a full renovation with new wiring, they won’t work in most UK homes.
You can always check the official Z wave alliance site to see exactly what products have been certified for your region. Then you have to track down a retailer for them.
when looking at light switches, read the conformance statements. If The device is called a “scene controller” or if it lists “controller replication” in the supported commands, it probably will not work with SmartThings, or at least not the way you expect it to.
If it is called a “binary switch” or “multilevel switch” or “dimmer switch” or “multilevel dimmer” there’s a much greater chance that it will work with SmartThings.
Table Lamps will work for some homes
Of course, if you’re already using table lamps, then you have a pretty wide choice of plug-in modules for either Zwave or zigbee that will work well with smartThings. Sometimes that’s the simplest route.
My house, in the States, was built in the 1950s and actually has very few ceiling light fittings. So I use a mix of plug-in modules and smart bulbs. I started out using the plug-ins, but after I got the Amazon echo working I really liked it for light control, and I switched to a lot more smart bulbs. Different things work for different people.
My one universal recommendation, regardless of the country that you’re in or the type of device you’re buying, is to only buy from retailers with a good returns policy. I personally don’t buy electronics from eBay in the United States. Too many counterfeits without warranty. But other people are willing to run the risk to save the money. So again, a personal decision.