There should be no problem having the chimney on the outside. What can happen is that cold blockages may form in the chimney pipe, preventing up-draught. This can be remedied by burning an ignition pad in the upper soot hole on the tiles stove, the air in the chimney pipe is then heated and the blockages disappears.
You can also install a Draft Booster, a flue gas fan mounted on the chimney, which you turn on when you light up the stove.
Chimney blockages are a relatively common problem in the autumn when you should put your stove into operation after it has been left unused for a long time.
