Filling in a space where a door has been removed

I have an arch way in my livingroom where a door used to be, i would like to fill in the space and make the wall conplete with no space at all also how do i hang kitchen wall units as i'd like to add a larder unit plus one wall init

BIRCHY

GOOD EVENING "K",
1.MAKE A WOODEN FRAME TO FIT INSIDE THE EXISTING HOLE,DEPENDING ON THE WIDTH YOU MAY NEED TWO FRAMES.PLACE THE FRAMES APPROX 10mm FROM THE OF THE ARCH AND FASTEN THEM TO THE INSIDE OF THE ARCH.CUT SOME PLASTER BOARD THE SHAPE OF THE ARCH AND NAIL IT TO THE FRAME ON BOTH SIDES,YOUR WALLS SHOULD BE FLAT NOW. PLASTER THE BOARD TO MAKE IT JOINT WITH THE EXISTING WALLS.LEAVE TO DRY.PAINT OR PAPER AS REQUIRED.
RE-LARDER AND UNIT IF DRILLING INTO BRICK USE RAWL PLUGS,IF USING ARCH SPACE USE PLASTER BOARD PLUGS.

HOPE THIS HELPS YOU,

GRAHAM.