Compatibility summary
Your United Kingdom plug may fit in Sri Lanka outlets, as both use at least one common plug type.
Plug comparison
United Kingdom plug types: G
Sri Lanka plug types: G
Both countries share at least one plug type (G and G), so some plugs may work without an adapter. Check your appliance.
Voltage comparison
United Kingdom: 230V, 50Hz
Sri Lanka: 230V, 50Hz
Voltage difference is within a range many devices tolerate; check your appliance label.