While you are waiting for your UTH if your house is generally around 70 or so, then you still do not need to use the lamps so long as you do not feed your snake. IF your UTH will arrive say with in the next week or two, I would not worry about it, so long as your room temps do not drop below 70 and you do not feed your snake.
If it is going to take longer than that to get the UTH, then you could use the lamps say just for the 5 days that you need for feeding time. Set it up and stablize the temp a day ahead of when you are going to feed, then feed the next day and keep the heat on for the next 3 days. Thus you have time to stabilize temps and to allow your snake to digest.
It is hard to stabilize temps using a heat lamp though, your only really way of adjusting is to raise up and lower down the lamp, thus giving more or less heat to the warm side.
Make sure that the type of thermometer that you are checking your temps with is a digital one. The sticky dial and strip ones are famous for being highly inaccurate, as much as 10-20 degrees either way. As well make sure that your digital thermometer probe is lying right on the bottom of the viv where the UTH will be and where the snake can burrow to, as they do like to burrow and when you get the UTH it will burrow to get to the heat.
If you temporarily use a heat lamp then place the probe inside the warm hide on the substrate as you will want to check the air temp in there as lamp only heat air.