Mould

@SophieOrman It shouldn't affect her diabetes directly, but obviously if it makes her ill then any infection could put her blood sugars up.

Hope you get it sorted as soon as possible. I've lived in a damp house and it's not nice at all.

You might try washing off the visible mould from any solid surface and using a dehumidifier to dry the air - though not too drastically as moulds produce spores when they dry out. If you dry clothes in the house then a dehumidifier beside them would be a good idea, also in the kitchen when cooking - good thing the larger ones are usually on wheels.
Moulds do affect general health and lower resistance to infections.

Also keep windows open as much as you can to keep fresh air circulating, you can buy mini humidifiers from b&q for about £12. Do you know what's causing it ?

As a surveyor (retired) I can say that its a very hard problem to get rid of, mould. It is a problem in badly insulated houses that are too tightly sealed.
Keep wiping it off, try not to let the house get too cold, avoid fan heaters. Use the ventilator in the kitchen. If you have an open fireplace try using it, that will dry the atmosphere of the house.
You are right, it's not a healthy environment for children generally, but I don't believe your little one is at any special risk

Absolutely keep the air circulating, even if it is only by having two windows open a crack, one at the front and one at the back of the house.

Water evaporates better in moving air, but then that water laden moving air needs to leave the house, via a window, door, vent or chimney.
- only fill the kettle as much as you need to, to prevent producing unnecessary steam
- sleep with the window open, even if it is only half a centimetre open
- cook with the lid on the pan, and the extractor fan ON
- open the bathroom window immediately after bathing or showering and don't close it until the room is dry, including towels
- never dry clothes inside, in closed rooms (best option is to dry them outside, old style on a washing line. If you can't do that, make sure the room has a good airflow via a window, or your tumble dryer is vented to outside)

Depending on the age of the house, they can be built of materials that need to breathe. Sometimes sealing houses up with double glazing and central heating can make the problem worse, by trapping the moisture inside.

I live in a damp cottage, and have been for the past 18 years .. Trust me when I say .. please don't go for the small cheep dehumidifiers they are just a waste of money .. the bigger ones often have a air filter in to remove mould spoors from the room. I do have windows open, but not all the time as I live next to a chicken farm .. trust me that 4 sheds containing 14,000 hens each gives off an oder that is so bad the mould disappears as a problem. I also run air purifiers that keep the mould away. Single glazed windows are good as you can just wipe off the water from them, sadly the silly double glazed windows are not good, the the extra damp in those rooms go onto the furnishings so cannot be wiped away.
Don't just pretend its not happening .. being pro active in removing the damp and any signs of mould will keep you healthy.
I take it your rooms are not centrally heated .. so try and keep them warm in the colder weather, we use the elect(no gas to the cottage) oil radiators to stop things freezing up. Regularly look into your cupboards and wardrobes .. as cold can quickly set in if your not on top of things. For the bed, we use an electric blanket to help keep it dry, always unplugging the blanket from the wall before getting in.
Outside walls will be the coldest and dampest .. so regularly check the for mould. Don't expect the council to be to fast in their response to your mould problem ,, Hope your sorted out soon

One thing I should have said - my brain since I took statins for three weeks is just away with the fairies - we saw a great reduction in the mould in a lean to kitchen when a thermostatically controlled radiator was put in there. It went from a black hole to a space you could work in, just by keeping the temperature up enough to prevent moisture condensing on the walls.