switching off boiler

hi im going to drain the ch system on my britony combi 100 to fit same rads and trvs on. i wanted to know how to shut the boiler down correctly to allw me to do this.

1. turn the control knob on the left all the way to the left which is off

2. do i need to turn the tap under my kitchen sink to stop water aswell?

3 what about the gas? does it need to be off? the tap for it on the boiler seems a bit doggy plastic tap thing. so if it does need to be off will it be okay if i just turn the main tap at the gas meter to off

thanks

Off on the control knob and drain down. No need to touch the gas or mains stop tap.

I'd pull the fuse out of the spur/plug as well just to be sure.