I have a room which has 3 separate light circuits if you will (each light has its own wall switch, they’re physically next to each other), but they all share the same permanent live.
This is what the live wiring looks like. Obviously each dimmer has a switched live running to the respective light.
Is there any reason this wouldn’t work?
Sorry, I’m confused by the diagram. What’s the circle in the middle? And is the L for live or for load.
Does each dimmer switch control a different light fitting? Or are they all controlling the same one?
Apologies, you can probably tell I’m not an electrician! 
The circle in the middle is a junction box. L is for live.
The plan is for each dimmer to controller a different light fitting.
I think my problem lies in the wiring, but I’m not sure what the answer is…
The permanent live is ok and powers all 3 dimmers.
Dimmer/Light No. 1 works as expected, turn on/off and with SmartThings - all good 
What happens with the 2nd and 3rd light fittings is they power on regardless of the physical switch position or status in SmartThings
A common live is fine. That is what you have to all your lights on a single floor anyway. It’s what happens with the other connections to the dimmer2s that count. Can you post a diagram showing the rest of the connections?
So I had a few days off and revisited - 2 out of 3 lights are now working, I must of wired them incorrectly!
The third light consists of 2 LED bulbs. When I turn the lighting circuit back on, the LEDs turn on but dimmer than usual. If I turn them on, the flicker for a second then go back down to a lower level. I can’t turn them off through SmartThings or the physical switch.
Is this a case for the bypass? The LEDs are only 2.5w each so 5w in total.
5w will be a problem. Especially if you run without a neutral to the module. I would recheck your wiring and then go for the bypass.
Bypass has fixed it now to get the Dimmers in the back box!
Thanks for your help