From what I hear they seem really hard to get rid of, but can't you just spray everything with a residual pesticide? Or do they not get affected by that?
A lot of pesticides today are actually human/animal safe. I use this one around the house to ensure I don't have spiders, or any other bugs.
http://www.doyourownpestcontrol.com/cyonara_9.7_insecticide.htm
I have not seen a spider or spider web in my basement since the very start of summer. It kills em really good, and any other bug.
You just need a pump container and you put about one ounce into a gallon of water. The directions say what concentration to use based on what you want to kill. I'd just spray all upholstry with it, carpet, baseboards etc. I can guarantee you wont have any other bugs either.
If heating the room at 50C actually works, just get a couple industrial heaters in there and a thermometer to ensure it will actually get it that hot (aim for like 60C to be safe), and lots of fans. Though I wonder how bad that is for the paint and stuff though, but meh, if they don't want to do anything then take it in your own hands and whatever extreme you have to do.