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The bigger ones like mine are supposed to be good up to 2-3 bedroom houses. As the room it is in dries, the moisture is drawn out of the others. If it's a shared house, have you considered chipping in for a communal one? The benefits will be shared anyway; clothes dry faster, house heats up quicker etc. Also, chances are if you only try to dehumidify your room, you will draw in moisture from the rest of the house anyway as soon as you open your door.
Although this one is well reviewed
https://www.amazon.co.uk/Pro-Breeze-Portable-Dehumidifier-Moisture/dp/B00NFRTVY6/ref=sr_1_4?s=kitchen-appliances&ie=UTF8&qid=1508754442&sr=1-4&keywords=dehumidifier