I think I need a dehumidifier

Is there any smell of mold if so it could be a leak.

Also you could have an airbrick to the outside wall to allow air to come in. We solved a problem is our home by putting one in.

Sod's law.....we slept with the window open a crack last night and no condensation this morning. The weather has changed too and there's not a drop on any window in the house.
I did notice moisture at the bottom of the front windows next door, so it's the house not us.
Anyway the dehumidifier is being delivered this morning and will be useful for drying washing if nothing else.
Using the water for plants is a great idea Hetty.

It's whirring away quietly in the spare room and I've just put an airer of newly washed clothes in there.
I put it on for a couple of hours yesterday and the water tank was half full when I looked.
Next test is to check the electricity usage on the smart meter.

I moved into my bungalow in March, and noticed condensation on the bedroom windows in November. There are trickle vents in the tiny window, as well as a vent in the capped chimney breast.

I bought a 20L dehumidifer from Aldi, but hadn't realised it had to be in an enclosed space, only able to use it in the one room. It collected 10L in the first night. Since then I've discovered the whole bungalow has a condensation problem, the plasterboard floors are covered in mould.

I am going to have a positive ventilation unit installed in the loft, the company is called Nu Aire.

www.bmstores.co.uk/products/fabulosa-interior-dehumidifier-rainbow-drops-3750272

Some times low tech works well! These have moisture absorbing crystals in them. I found one on each window sill made a difference and they’re only a pound or so each. You can get in pound shops, home bargains, B&M etc. you leave them sitting there and replace every few weeks or so when full. Wouldn’t replace a dehumidifier perhaps but you can’t have one of them in every room and these do help.

Teacheranne
I am convinced but DH isn’t. What company did you use?
Shandy hope it works.

I have had the machine running in the box room with the laundry for a few days now.
The washing dries quickly and so I only really need to use the tumble drier to fluff up towels now. The rest of the house already has less condensation on the windows. DH has started decorating again so that is a factor.
Electricity usage has remained the same, maybe even a little down which is good news. I also have a free source of water for plants and am trying it in the iron too.
I'm very happy with my purchase.

Shandy57. We’ve installed a NuAire heat recovery system in our new build. Ducting throughout. It should help to keep humidity down to a healthy low of 60.

I live in Cornwall, which is a very humid county. Damp in houses is very common. Humidity in our little cottage is 71 at the moment because the dehumidifier is on but there’s still some condensation on the windows. We have 2 going some days. Humidity level has been as high as 80. Can’t wait to get into our new house.

I'm green with envy muse! I haven't got any further with my installation with this roof blowing off lark, I hope to do it later in the summer.

The issue you describe is common in the UK & features a lot on Landlord forums where tenants are involved.
If you dry washing on radiators, try to stop doing that as it exacerbates the problem.
When you bathe or shower, keep bathroom door closed during & after. Crack window open.
Keep lids on boiling pans in kitchen.
Crack windows open or ensure trickle vents in double glazing are open.
Try using an airing rack in bathroom overnight with damp washing on it, so that the worst of the damp dries off in that space with door shut. Stand airer in bath if space is limited.
If you use a dehumidifier in a particular room, shut the door on that room whilst it’s in use. The dehumidifier won’t cope well if door is open. Too much to do.
There are special vents which can be installed to completely overcome this mould & condensation problem. Some companies who specifically deal in these vents usually offer a free survey & recommend options,
Regardless of winter, houses need to be aired. Today is sunny (for a change) so my bedroom windows are open & the door is shut.
Use a preparatory solution for mould on black patches and allow to thoroughly dry. Paint or emulsion over it as necessary.
There is lots of info on the internet if you Google for “condensation causes” & surf the sites for advice from there. There’s plenty there to help you.
It’s a demanding problem which takes application & energy to overcome and keep under control.
I’m sorry you have this worrying problem. It’s an absolute pain but can be overcome.

I bought a few over the years and one of the best was from Argos, own range called the Mk 9 , I can't see they are still the same ones as I purchased it about 10 years ago they were about £90+ but well worth it it has survived a house move and I put it on overnight in the conservatory at this time of year and keeps the windows mist free and stops my blinds going black . Ebac is another good make that was the first one we had lasted 30+ years we gave it to my daughter when we moved and to my knowledge it is still in use.