My sewing machine/cutting table is against a wall because when I am piecing or quilting the wall 'holds' my quilt on the table.
If it was in the middle of the room my fabric/quilt would always be falling off the edge. My room isn't large enough to place it in the middle. If it was, I would still have it against a wall.
My ironing board is set up where ever I need it to be set up, depending on what machine I am using. My room isn't large enough to have a 'permanent' ironing area. When I don't need to iron I can take it down and stash it behind the door.
Set things up whichever way is convienient for you.
If it doesn't work. Its easy enough to move things around.
Happy Quilting!