Quick answer
Replacing a like-for-like switch is minor work and can be done by a competent homeowner. However, many smart switches require a neutral wire which older UK wiring does not have.
Replacing a standard light switch with a smart switch is technically minor electrical work, which means a competent homeowner can do it as long as it is a like-for-like replacement — same position, same circuit. However, most smart switches require a neutral wire (a blue wire in the back box) to power their electronics. Many UK homes, particularly those wired before 2000, only have a switched live wire at the switch position and no neutral. Before buying a smart switch, check inside your existing switch back box to see if there is a neutral wire. If there is not, you either need a smart switch designed for no-neutral wiring, or an electrician to install a neutral drop. If in doubt, always call an electrician.
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