It is a useful exercise to think about the layout of a room and how it will be used before deciding on the location of the fireplace. It is worth checking that the arrangement of the doors, windows and fireplace will accommodate your furniture layout.
The best place to site a chimney is in the centre of a house where the maximum use can be made of its heat storage and ventilation characteristics but this choice may be over ruled to maximise the living area.
The fireplace recess and the chimney can be sited on an external wall, a party wall, an internal partition wall or be freestanding as illustrated.

Siting the Fireplace
It is worth checking that the arrangement of the doors, windows and the fireplace will accommodate typical furniture layouts.
Most layouts for rectangular rooms will have the TV set alongside the fireplace as it is difficult to arrange two ‘focal’ points.
Fig.1 shows a typical arrangement for the fireplace in a semi detached house centrally placed along the party wall.

Fig. 2 shows another typical arrangement with the fireplace in the centre of the wall below the ridgeline of the house.

Note that the door and window openings are sited away from the fireplace.