Not sure about the Hue dimmer switch - but only just seen this thread.
This was the exact issue I had when I first started using Smartthings (UK as well). The Solution I found was to us Z Wave.me’s wireless wall switches. They are awesome and can be fitted with loads of different faceplates and buttons in plastic, metal and glass. See here a selection of various finishes that I’ve used:
I created a device type and app (below) that can be used to make these control whatever you want.
For UK plug sockets - it’s not an easy solution but you can use the Fibaro Relay 2 x 1.5Kw to make these part of your automation system (or just use the smartthings plug socket if you don’t mind the budge)