A de-humidifier will dry out the wall, but if not used correctly it can and does cause damage as it removes all the moisture from the plaster / cement thus causing cracking. A lot of new home employs this technique to speed up the drying process so the builders can start second fixing / painting etc (cowboys!)
To dry a wall out, turn the heating on for a few weeks (start off slowly and day by day gradually increase the temp… if you turn of the temp full blast it will also cause cracking.
are you sure you have found the leak...did you seal the brick work?