I disagree. Heat lamps suck out humidity which causes just as much of a problem as low temps. Not to mention they burn out quite often and that can get costly.
OP: You need a thermostat to control the UTH. The cheapest model is the reptitemp 500r. If you have a probe thermometer, place it on the glass above the UTH, under the substrate. If the temperature gets above 95* then unplug the UTH.