Have a look at the floor for draughts. Our old methods of construction were pretty shocking. Look out for gaps underneath the skirting boards. Our walls are u

Have a look at the floor for draughts. Our old methods of construction were pretty shocking. Look out for gaps underneath the skirting boards. Our walls are usually a double skin of brick and there will be air bricks to allow the gap between to dry out. Then you have floor/ceiling joists, probably with gaps around their ends. On the joists you will have floorboards, again with gaps between them. On the boards you will probably have some rubbish underlay and then carpet. Around the edges the walls will be finished with skirting boards. Over time the floors will sag. You only report "one" hell of a draught coming from somewhere. There will be lots of draughts!