Good info there from @jelockwood. In case it helps, I use the Genius Hub system which is very similar. One key point I had to consider was the number of radiators we have and the number of separate “zones” I wanted each with differing schedules or modes. At the time, I chose Genius Hub as it was the only system I could find that supported more than 10 zones. Maybe that’s not an issue for you though and maybe Tado support more than 10 zones now.
Prices appear similar: £130 for the Hub, £60 for a Dual Channel Receiver (to replace your existing controller - dual channel as one if for hot water and the other is for the central heating) and then £60 for each TRV. You can add optional room thermostats for £70 (the TRV isn’t the ideal place to measure temperature) and movement sensors for £45.
This is a Z-wave system that runs on a separate network in parallel to SmartThings so you can’t directly use your existing door and motion sensors. You can use the community Heat Genius Hub integration however to link in your existing sensors and then use webCoRE to enhance automation. The Genius Hub has native smarts of its own of course including “Footprint” mode that uses its own movement sensors to turn heating on and off when rooms are unoccupied and which can learn usage patterns for each day of the week to pre-heat rooms etc. I find that very useful.