Hi, looking to change my 4 gang switch, what I have is 4 grey wires, each with a red and black wire, I've been told by local sparky that each red wire goes into COM, and each black wire(with small red sleeve If that's relevant) goes into L1. However at the moment only the 1st and 3rd switches are wired like this the 2nd and 4th have red wire in L1 and black wires in COM. All switches work the correct way as it stands, I am aware I have to add earth to New metal plate. Another local sparky suggests just copying as it is now, or are both methods correct. Any advice appreciated, I've changed lots of other switches and sockets but don't want to risk anything on my last one.