Well on the original switch it had three connections on each of the black plastic bits - L1, L2 and C, and red wire went into L1 and black wire went into C

On the new one each black plastic bit has L1, L2 and the funny arrow bit, so I wired up like the original - reds in each L1, blacks into each "funny arrow", and got "funny" results lol.... IE, the flickering, really dim/low power....

I reckon the actual ceiling light units are fucked aswell, as when (ages ago) the dimmers stopped working on the original switch, there was a "POP" noise and the lights went out (tripped the ground floor light ring on the breaker board) and after turning back on the dimmers didn't work. However, it's done it several times, and now only one of the three light "sockets" in each light unit work. Put a new bulb into the other two sockets and they don't work. So each light unit has only one working light socket and no dimming.