Low level heat source for tiny room

Another option if there is a way of hanging it is a good old fashion IR heat lamp. This type of thing

https://www.amazon.co.uk/Luxvista-Adjustable-Suspension-Infrared-Brooding/dp/B0C3CYZD24

Not very elegant looking but might do the job (fitting above doesn't include bulb).

250W would use one unit of electric every 4 hours.

I have something like this for drying clothes:

https://www.amazon.co.uk/Trintion-Foldable-Electric-Portable-Power-Off/dp/B0DM8JL78X?source=ps-sl-shoppingads-lpcontext&ref_=fplfs&psc=1&smid=ASXNODVM5DP4I

Theres a heater at the bottom which blows warm air up through the "tent". Does a great job drying. I have it in a room with no heating.

Could be what you want as you dont want to actually heat the entire room, just the area where the clothes are.

A side effect of a heat pump dehumidifier is that they do slightly warm the air.

Using one to dry hung clothes is supposedly more energy efficient than using a drier.

Does the ventilation system recover heat or is it just extract or wha?

so then the de-humid option might be best, or the "tent"

re this

Fan heaters tend to have higher consumption

most fan heater have 2 heat settings:

1kW always on

2 kW with stat

I have one of these from lidl keeping a room at 12 degrees, couple of kWs each 24 hrs

I have another which is 1/2/3 kW, 1 always on, the other two on the stat

elec consumption is power in kWs by duration in hours

the tubular ones are 120 w, which may not generate enough heat quickly enough so the heated air may just get extracted before it does any work

No, I said heat-pump. There are two elements to a heat pump dehumidifier, the evaporator and the condenser. One gets hotter while the other gets cooler - so water vapour condenses on it out of the air and is collected in a tank. Even though you might think that the heating and cooling would balance out - being in the same room - they don't, because the cold condenses water and so some of the temperature differential between the two circuits is reduced, ending up in the water and resulting in a net warming, as well as the electric motor adding some warmth.

Using a heat pump dehumidifier to dry clothes uses less energy than a heat only tumble dryer, which is why there are condensing tumble dryers which incorporate a heat pump.

Is a dehumidifier cheaper than a tumble dryer?
In most cases, although a dehumidifier needs to be turned on for longer compared to a tumble dryer, it’s far cheaper to run. Over the course of a year, you could save as much as £376 by switching to a dehumidifier.

https://www.householdmoneysaving.com/dehumidifier-vs-tumble-dryer/

So extract only system then.

Buy a dehumidifier.

I have this one. Around 160w peak power and will mitigate against any existing moisture damage in the room as your already using it to dry clothes. They're brilliant. 3 kids in the house, it's always used

https://www.meaco.ie/meacodry-abc-10l-compressor-dehumidifier/

It does emit heat alright as someone already explained above. Have to remember to empty the dehumidifier every day.

I hang clotheshorse in the smallest room in the house with one of these. Right job they are.

Kinda strange you feel a draught here assuming the vent is extracting, the draught should go into the room.

There may be a reason for that draught. Dehumidifier will help mitigate any moisture issues