I don't know your full situation. But, I would still say that using the fact that you did all the work to find the house is not the best ground for choosing the room unless you had already decided this with your house-mates prior to looking.
Explain the problems that you are having with the room and admit that you think it was a mistake to choose that room. Ask if someone else is willing to try and take that room. If nobody likes it, at least ask them if you can do swaps at the end of term or if each of them will pay a couple of quid more per week to at least help you guys lessen the cost of that room for someone else to move in (as it must be bad if none of housemates will take it).