Change switch to dimmer confusion

[Spadez]

Right in the middle of this job and realised I don't know what I'm doing.

I currently have a Crabtree switch on a light in my living room. The switch had three wires on it which feed into terminals on the switch labelled:

L1, L2 and L3

However on my new Crabtree dimmer switch the terminals are labelled as;

L1, L2 and a then a wavy line with a diagonal arrow through it pointing to the top right.

Am I to assume I should put L1 in L1, L2 in L2 and put L3 in the terminal with the wavy line and arrow?

Any help would be really appreciated as I don't want to blow anything up.

 

[PrenticeBoyofDerry]

So is this a two way switch then, meaning there is at least one other switch that operates the lights. If so is that also a dimmer or a standard rocker or pull cord?

Also are the lights you intend to dim, suitable for dimming? Not all are!