Hi there before I go and purchase either a sonoff mini or shelly 1 can someone please advise which of them is better suited for UK wiring. I’ve seen video of a shelly 1 being installed in a ceiling rose but I want to put mine behind the light switch if there is enough room. If so are there any diagrams on how to do this.
Try their Shelly Support Facebook group. They answer very quickly over there to all kinds of wiring questions.
I have several of Shelly2.5s behind my roller shutter switches, one was really tight because of all the wiring but usually there should be more than enough room to fit a shelly behind a switch in the wall.