I actually have a similar problem to yours. First off, keep the thermostat! You've got to have a thermostat no matter what heat source you are using.
Right now I have my BP in my parents basement and it stays a very consistent 70-75 degrees down there. I actually had to go back to using a heat lamp and UTH to try an keep the warm side temp up. I have a Reptile Basics radiant heat panel on the cool side which is on a rheostat right now. So far it's been working all right for me. The only thing is the heat lamp kills the humidity in there so I set up a humid hide since she is getting ready to shed again. I'm moving into a new apartment soon though where I should be able to keep the room temperatures at a better level.
Good luck finding a way to get your temps regulated!