You can only use two speakers for rear channels, and they should be behind the seating  area  and in line with the TV.    For that reason, speakers along the back wall, positions “1” and “?” are the better choice.  Position 2 isn’t really going to work  well, even though it’s behind a seating area, since it’s even with the TV.  The goal isn’t to cover the space with sound, but have the sound come from the right location, corresponding with the action on the TV.  Because person 2 is at an angle, off to the side, he’s not going to get the ‘right’ experience anyway.  In the same way that  he’ll experience the front speakers from an angle, it should sound relatively correct to hear the rear channels the same way...as if he/she is witnessing the action from the side.  Not idea, but better then mixed up sound for everyone.

If possible though, I’d move “?” out of the corner about 3’-4’ in, so it lines up with speaker 1.  This will mean make the audio come for a more correction location, if that makes sense.  Another alternative would be to put the TV and Beam on a swivel mount so that it will turn and face the center of the couch with the surround speakers in the middle of each walls.  That will help out person 2 at the expense of person 1...and the surround will be off a bit.  Best seats then will be near the corner.  Not sure I like that last alternative.

That great, thanks for your reply. That makes sense so will go with your first option of in the corner. Last question, the wall behind the sofa is a separating wall with our neighbour. Would a wall mount be ok or would there be quite a bit of sound transfer through to next door? Or am I best getting stands and having them a bit away from the wall? Thanks.