ok middle speaker above the TV surround speakers in either corner at the back in line with sofa, facing the TV and pointing slightly down (15deg or so)
but what about the from 2 speakers, where are they supposed to be (30, 45 etc 25/50/75cm from tv...) and turned to directly face the sofa?
Technically, your surrounds are supposed to be on either side facing inward 'even' with your primary listening position......not in the back.
As for the fronts?? It depends on your room and what you want to do. Some put the mains fairly close to the TV, while others will separate them significantly more. My fronts are more than 10 feet apart. Your roomsize and preferences will dictate their separation. If you do position them near your TV, make sure your speakers are shielded or it will ruin your picture.
The general rule is 1 1/2 the width of your screen for the fronts. With music you want them further apart for imaging but with home theater closer in gives more presence to the screen.
Anyway, your room will dictate speaker positioning more than will screen size. Room Size/shape and seating layout will play a more important factor in speaker positioning.
They should be on the sides even with your primary seating position facing in at the listener. And no, they shouldnt be facing the TV. Why does your TV need to hear them?
do the rears have to be equal distance away from the sofa as in my room the sofa is nearer the wall on the left id like to put the rears in the corner at each end but that would mean one side would be nearer the sofa than the other