Replacing a single switch with a dimmer

[mulder57]

Help !!, i have paged thru various sites and cannot seem to find the answer I need so I hope someone can help me.
I want to replace a normal switch in my lounge with a dimmer switch.
The wires coming out of the wall and into the normal switch are - Red , Black (with green sheath), Black (with grey sheath), Earth (green/Yellow) connected to backing plate in the wall.
The above are wired into the normal switch as follows: Red goes into 2-way, Black/Green goes into 1-way, Black/Grey goes into Com.
My Dimmer switch has connectors marked - Variable load, L1, L2, and Fixed load.
Can someone advise which wires go where ??

 

[ban-all-sheds]

Is it a 2-way switch?

 

[mulder57]

Yes it is.
Thee are 2 switches in the room, the other is a double switch which has a dining room switch on as well. I am not touching this one, only the single one.

 

[ban-all-sheds]

If you look at the Wiki article on 2-way switching, and see how it works, or rather see the different ways in which it can work, you'll realise that you need to look at the other switch to see what cables are there, and therefore work out which conductor is which at this switch.

Also, before you get too far into this, will you be happy with the way that it will work? If the lights are off and you turn them on at the switch then they will come on at whatever level the dimmer is set to - if that's not right then you'll have to go to the dimmer position to change it. Might you be better off putting in a proper 2-way dimmer setup?