You need to remove some of the aspen, your UTH can't do its job through that much aspen. I have found that 1/2" or less is best.
IF the room your cage is in stays above 75 degrees then a heat lamps isn't necessary. a UTH will be enough. UTH MUST be regulated by a thermoSTAT and monitored by a thermoMETER. unregulated UTHs will get to to 150+ degrees F more than enough to burn or even kill a BP.
UTH's do not change the temperature of the air in a cage so if the air temperature falls below 75 you will need a heat lamp to increase the air temperature.