It is permitted to install replacement light switches in the UK. The entire electrical system of a house does indeed have to be at a minimum checked by a qualified electrician and this mainly applies when rewiring a house but replacing a switch or light fitting does not require this. Due to this other products like Fibaro, LightWaveRF, etc. can be bought and fitted by end users.
The fact that all Lutron’s other product lines i.e. Homeworks, RadioRA 2 and RA2 Select are available in the UK shows Lutron are already experienced in dealing with the required wireless, power and safety differences. It also shows there is an established demand for Lutron’s products sufficient to justify this on economic grounds and I don’t think anyone - not even Lutron would argue differently for Caseta. They have even done different form factor smart wired switches for the UK and EU market for the Homeworks and Radio RA2 product lines. (RA2 Select uses the existing Pico remotes, for which they also do a European wall mount kit.)
The are even UK and EU versions of the Lutron Connect Bridge for Homeworks, Radio RA2 and RA2 Select complete with HomeKit support. So there is very little work left for them to do to make a UK/EU version of the Caseta. Note: This does not mean the amount of work is insignificant - it is significant but comparatively a lot of the work has already been done for the other product lines which after all use the same Clear Connect technology.
So I am sorry but I do feel insulted by Lutron as they clearly must think the UK and EU are too stupid to use Caseta. If you do have any contact with Lutron and via that are able to get them to respond with a valid reason then I am more than willing to apologise but as someone who previously worked for a technology importer and does have a good understanding of the issues I currently cannot see this.
I have been looking for years for my ideal smart lighting solution which would duh! be Lutron Caseta and so far no-one else has come close enough. As far as I am concerned yes this does make me picky but it also means no-one else has come up with an adequate solution for the UK/EU whereas a gazillion products many almost as good as Lutron Caseta exist for the North American market. I just before Covid-19 lockdown did establish contact with a European company which is working on a new product which still is not as good as Lutron Caseta but sounds close enough to be an acceptable second place choice - even at a much higher price. Price to many will be a deciding factor but with so few adequate options in the UK/EU and the fact we are used to being ripped off mainly by US companies that will not be a blocker to me. I had even accepted a willingness to replace my existing 2-core plus earth with new 3-core plus earth to provide a dedicated neutral. (Another reason Lutron Caseta was so perfect an option as it supports 2-core plus earth wiring.) The upshot of this is that Lutron likely will miss the boat and lose out on a big potential market, not just me.
If Lutron and other misguided Americans think we dumb schmucks in the olde worlde are not interested in smart lighting products I would counter with the humongous success Philips Hue has had and point out they have been successful not only in Europe but also the US and the rest of the world and are the leading smart light bulb brand globally, and by the way they are a Dutch company.
Lots of Chinese firms are producing smart lighting products for both the EU and the US. Why are US firms apparently incapable of doing the same especially as their products are typically made in Chinese factories? (The aforementioned Chinese products are not as good which is why I am not using them but they get closer each year.) Terncy seem better than Xiaomi/Aqara.
Perhaps it needs Google or Amazon to buy Lutron and give them the kick up the backside they apparently need. (Not my preferred solution, but it did result in the Eero WiFi product finally being made available in Europe.)