Welcome! Sounds like an interesting project. 
Because device selection does vary by region, I have moved this to the UK section of the forum so that you can get UK â specific responses.
From the initial description, my guess is that youâre going to end up going with fibaro kit, which are in wall microcontrollers that work well with SmartThings and come in a number of different models with different features. These are very popular in the community, and readily available from the various online specialty retailers.
For example, @anon36505037 has done his entire house with Fibaro devices, and may have more specific advice for you.
Iâm also going to include a link to the UK lighting FAQ which covers a wide variety of options available with UK devices, but again from what you have described already, I am guessing the Fibaro micros or one of the other microcontroller brands like Aeotec or Qubino will be the best match. But you might take a glance at the FAQ just to get a sense of what some of the options are.
Also, before we go any further, do you know if you have a neutral wire at the switchbox in these locations? In the UK this would normally be called a âthree wireâ set up, or a blue wire. This also affects the potential device selection, although several Fibaro models can work both with or without a blue wire, one reason why they are so popular.