Actually if the wiring is in good condition; there's nothing about using a dimmer that is 'unsafe'. All that's happening is the small amount of current is energising the actual switch for wifi even when the lamp is fully dimmed. This small current flowing through the circuit isn't enough to turn on the lamp but it still flows through the lamp to the lamp's neutral and back to the switchboard. In fact this is how Lightwave's dimmable switches operate. Although not always a requirement, almost all switch circuits in the uk will have a ground wired to them. This is terminated to the backbox (if metallic) to ensure that the metal screws on the faceplate are earthed. This safety earth connection can be utilised to provide a ground connection to the dimmer switch if it is not doubly insulated and requires an earth connection. Also there is no such thing as a "lighting ring main" all lighting circuits are radial in the UK. Only socket circuits can be rings and this is a throwback to post war wiring where we put them in to save copper. Rings are a pain in the backside and inherently unsafe. On large buildings we tend not to bother using them anymore as they are often more expensive to route on modern developments where you need a-lot more sockets than we put in in the 1950s, and if a ring is broken for any reason (say someone badly terminates a socket) then you can end up with two radial circuits fed by a circuit breaker that won't trip for a current the wiring isn't rated for.