First attempt at some electrics and need some pointers.

Hi all.

Attempting to put an LED/heated mirror up in the bathroom.

I want to run the mirror to its own switch, so that we can turn it on/off independently of the downlights.

So far i have connected the mirror up using 1.5 twin and earth (no earth connection on the mirror so ignoring that part), and run the cable to the existing switch but not wired into it yet.

The existing one gang switch (pictured) I intend to replace with a 2 gang (also pictured).

Currently there is just the one cable running down from the loft, Live into com, neutral from L2 and earth. In the loft a junction box that then leads to the 4 downlights.

I know that I can easily enough put the existing wires into COM1, L11 and the earth.

Im just a bit stumped on how I then go about getting the mirror to link into this.

Any advice much appreciated and thanks in advance.