Most smart switches require a neutral in the switch back box. Until now the only option was to consider expensive rewiring. Now there is another option to consider, these switches have been designed for the UK market and whilst not cheap they at least offer a choice.
https://wifi-smart-home.co.uk/smart-wi-fi-light-switches/21-no-neutral-one-gang-wifi-switch
https://www.amazon.co.uk/dp/B07Z373K81