Condensation occurs whether it is raining or dry outside. Condensation and mould growth is a sign that the air in your home is too wet.
Ventilate your home and allow air to circulate, use trickle vents and shut kitchen and bathroom doors when they are in use.
Produce less moisture by using correct lids on pans when cooking, venting your tumble dryer and avoid using paraffin or flue less bottle heaters. If possible don’t place furniture against external walls.
Insulate and draught proof your home, using draught excluders around window and doors including keyholes and letterboxes, loft hatches and electrical fittings on walls and ceilings. Efficient use of heating, keeping at a lower temperature for a longer time rather than higher for a shorter time.
Mould spots and spores can be removed using antifungal wash available from local DIY stores.
If you want a cheaper alternative you can use a weakbleach and warm water mix - always follow the instructions
If this doesn’t take the dampness away it could be another issue like: