I concur with what he said..
the red and black from the twin and earth at the lower hall switch need to go into L1 and L2 ( ie the bottom 2 ) of a 2 way switch, and the single red into the COM ( ie the top one.. )
as for the "flickering" I can only assume it might be caused by the live at the upper stairs 1 gang being in the wrong hole..
if it continues after doing the above then swap the 2 ringle reds over, but leave the red and blue from the 3 core where they are..
the red and black from the twin and earth at the lower hall switch need to go into L1 and L2 ( ie the bottom 2 ) of a 2 way switch, and the single red into the COM ( ie the top one.. )
as for the "flickering" I can only assume it might be caused by the live at the upper stairs 1 gang being in the wrong hole..
if it continues after doing the above then swap the 2 ringle reds over, but leave the red and blue from the 3 core where they are..
