Black mould on celing and walls

[Abubu]

Hi,

We have horrible browny black mould in spots on our ceiling and walls. Mainly in the corners but every so often in a random patch.

We have bought a dehumidifier (although to be honest probably don't have it on as much as we should). We use the tumble drier more and try not to leave washing out too much.

I don't understand what we are doing wrong?
What should I do to kill it before I paint over it?

Thanks!

You can buy mould and mildew remover from places like wilkinsions.
Wear gloves and a mask though.

When we had we were told to have a window open for a while everyday and having the dryer on would probably make it worse because of moist air but hard to avoid in this weather.

Are there any water pipes in the walls?

Our neighbours had a leaking pipe and that gave our walls damp patches.