Barely had the heating on lately, found small patches of mould

[AmberGer]

I was cleaning today and dusting windowsill in ds bedroom. We've had the heating on for about an hour a day. There are patches of mould on the corners of the windowsill next to the window.
Is this because of damp?
We've never been stingy with the central heating until this year.
Do I need the window open more?
The heating on more?
I don't know what to do.
It's was only a small patch and I have cleaned it off but I don't want it to come back or get any worse.

More air and more heat.

You need the windows open more and the heating on more. There is a lot of moisture in the air at this time of year. A lot of people are going to be experiencing problems in their homes by not having the heating on.

Yes it's because of damp, and yes you need to open the windows. You might find that airing during the day is enough to prevent mould without extra heating, although of course your house will be colder with the windows open. What temperature is your house now?

Yes more ventilation and heat needed. In the mornings now my routine is to go round and open all of the windows and the front door, wipe the condensation off the windows, then make a brew and drink it to warm up, and by the time I've drunk it and got dressed I shut all the windows and doors and put the heating on for a bit. I open window when cooking and showering too.

Spray it with a strong mould and mildew remover spray or it will just keep coming back.

White vinegar kills mould. One part white vinegar to one part water, spray, leave 5 minutes, wipe.

Vinegar is preferable to bleach because mould reacts to bleach by going deeper into the wall/fabric/other porous material, it will then come back. This reaction doesn't happen with vinegar for some reason, so the mould actually dies rather than hides.

I know people are going to laugh at that, but it's true. I know this because I restore vintage prams and have done a lot of research into restoring mould damaged materials.

We're not using the heating much, but we are opening the windows when we can, and dehumidifier is on when washing is on airer. And we have trickle fans in the bathroom and cellar.

Make sure your trickle vents are open if you have modern windows. It's the little slot at the top of uPVC windows

We have newish windows (10 years old) but they don't have trickle vents on them.
Thanks for the tips