Damp/Mould on ceiling. What could be the cause?

I've recently bought a house and since we moved in ~12 weeks ago some damp and mould has been forming in the ceiling of the en-suite off the main bedroom. I'm trying to get to the root cause of it and will give you as much info as I can. Apologies in advance for the wall of text. The house is a single-storey south facing bungalow and the en-suite is at the back of the house.

We bought the house in the summer so when the inspection was done by the engineer there was no sign of any damp issues due to the dry, hot weather. To be clear there are no damp issues in any other room of the house.

The weather was pretty wet in the weeks following our move-in and after a few days of continuous rain I noticed that there was a golf-ball sized hole in the fascia, exactly where the worst of the damp is. I attributed the damp to water ingress there and have since lined up someone to replace the wood and gutters next week. In the meantime though the damp has continued to spread even though we've had little rain in the past few weeks. Also the roofer has said that he doesn't think that the hole would be responsible for the damp in the room.

In the past few days I've really noticed that the bedroom now even smells and feels damp. When I wake up in the morning the top of the duvet can actually feel clammy to the touch. However there are 2 other bedrooms all along the back of the property and there is no sign or smell of damp in either of those rooms. In addition to that, the water storage tank is in a crawl space in an attic conversion right over the main bedroom and there's a kind of musty/damp smell in there, but I guess that's probably somewhat normal given that there's a big plastic tank of water in there with pipes coming from it. I couldn't see any obvious issues there either.

The en-suite is carpeted (I know... being replaced with tiles soon) and has no extractor fan. There is however a small window with a trickle vent in the room and I do try to keep the window open as much as possible. The bedroom itself is unaffected in that there's no obvious damp on the walls or ceilings but definitely a musty smell. There is a large double door and window in the room too which can have heavy condensation in the mornings. There's only a small wall mounted electric heater in the room for heating.

Finally there doesn't seem to be any water pooling outside the walls or that on wet days and the site is about 10 feet above the road so the drainage is good.

I'm just hoping that it's a combination of the carpet absorbing the moisture in addition to a lack of good heating and ventilation but I'm more concerned that it's something more serious. Anyone have any suggestion into next steps of investigation?