Smart Power Socket (Wifi Wall / Retrofit Socket by BG Electrical)

As far as UK options, there are some new ones coming on the market. In particular, the Aurora AOne line looks interesting. Those are zigbee, so they have a direct integration with the smartthings hub.

The in wall outlet from their line isn’t in the official compatibility list yet, but there are some community members looking into it.

https://www.smartthings.com/gb/products/-/filter/brands/aurora