Have you tried negotiation with the person in question? They have the ability to lower the bandwidth used by LW whilst others are obviously using the internet. Example, they could run it with more bandwidth whilst everyone else is sleeping or not in the house. Unless they are non-negotiable & selfish. Could block ports above 1000 for example (via router port settings). However would be nice to see a compromise made. Such as them limiting how much bandwidth LW is using whilst housemates are at home. They can do this via LW's Tools -> Options -> Speed /Downloads/Uploads, or for LW 5: Tools -> Options -> Advanced ->Transfers.

Oh .. I notice you are using same ISP as me. I sometimes limit the bandwidth used at various periods of day if my monthly total is reaching my maximum. Peak hours is my main concern since the maximum is about 40% less than off-peak maximum. ie: from midday to 2 am. Though your concern seems to be mostly over the actual bandwidth used at any time which is starving other housemates of using the internet bandwidth for browsing, etc.