For a decent overview of what’s available in the UK, I’d suggest a look at:
I’ve no connection other than being a customer, but they do have a lot of help materials to show differences between options.
I’ve been automating parts of several homes for over 25 years, and have tried several approaches. My personal opinion is ‘smart’ bulbs have too many problems, and replacing the switch is always better as that way you have a single point of control and can use any bulb.
‘Smart bulbs’ cram a bulb and control radio into a very small package meaning they may not be as bright or as reliable as separate devices. The main problem though is they can easily be switched off by other family members rendering them useless!
There are rather inelegant hacks to hide the mains switch behind a ‘smart’ switch, but unless you are renting so can’t make any changes, the result is a bit ugly:
Worse, cheap and nasty no-name bulbs likely come with a big security health warning and a poor quality app both connecting to an unknown off-shore server to avoid NAT firewall issues.
For a scary view from a well respected security researcher, look no further than EMF which has a lot of background to ‘smart’ bulbs:
I don’t use bulbs, but Ikea’s offering is a lot cheaper than Philips Hue and both are supported.
In the UK, switches are installed in single gang back boxes which can be as shallow as 16mm, and only have Live and bulb - no Neutral. This means the best place to install a ‘proper’ switch is behind in the ceiling rose as this is the one point where Live, Neutral, switch, and bulb wires can be accessed.
Low-cost Sonoff devices work well with the alternative Tasmota firmware installed, but their nice looking glass wall switch needs a Neutral wire, so isn’t that much use for UK lighting without rewiring with triple and earth.