Hey, the easier way to do it is take a phase wire from the DB to the light switch furthest away and connect it into the common of the switch. then take 2 more brown phase wires from that switch to the intermediate. Make one L1 in and the other L2 in.
Next take 2 more brown phase wires from the intermediate to the other switch and connect into L1 and L2 respectively, so that they match up. then take a phase from the light to that last switch and connect into common. Then finally take a neutral and eart from the DB to the light. then take and earth back from the light and connect it to each metal back box, taking an earth link from the back box to the earth on the metal plate switch.
Finally go back to the intermediate switch and put a link in from the L1 in to the top of the emergency key switch, and a link from L2 in to the bottom of the emergency key switch.