It's the beginning of the condensation season, Lostboy.
Of course, this coincides with putting the heating back on.
Your old windows used to keep a good flow of ventilation through the room. Use the trickle vents on the new windows. Keep the room moderately heated and ventilated.
Essential to fix the guttering. Eventually it'll damage the brickwork. Also, a damp wall is colder than the dry ones, and a cold surface attracts condensation.
If it's cavity brickwork, then consider filling the cavities. It's very beneficial, and subsidised by the local council.