COOL! That is one good-looking piece of mopani.
I can give you a short list of the equipment I've been running since January, shortly before my corn arrived. I'm happy with the equipment I have. No complaints here.
Zoo Med digital thermometer:
http://www.amazon.com/gp/product/B00...=ATVPDKIKX0DER
A probed digital thermometer on the warm side, affixed with aquarium-grade silicone to the bottom glass over the center of the UTH. Make sure you use aquarium-grade silicone (example:
http://www.amazon.com/00688-Househol...6445525&sr=8-5). This is very important. Also, it'll need two days to cure, during which time your corn will need somewhere else to stay, and the UTH should be unplugged. I've read that others have successfully used Blu-tak and hot glue instead of silicone, but these substitutions were only about 50% successful for me. The silicone was 100% successful.
Exo Terra digital combination thermometer/hygrometer:
http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1
A probed digital thermometer-hygrometer combination on the surface of the cool side. I suspended it in location. The suction cup is positioned approximately an inch above the probe, and with a drop of distilled water in the cup it sticks quite well. I pressed down and moved it around on the glass until it held, and this helps remove any excess water in the cup. Easy to do.
Since you already have a digital hygrometer, you may just want to opt for two of the thermometers above.
Hydrofarm MTPRTC digital thermostat for heat mats (now called Jumpstart):
http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1
I think with enough substrate you can, in theory, insulate the surface enough for it to be safe for your corn. However, a burrowing corn can reach much hotter temperatures deeper down in that gradient. Temperatures that are not safe. Temperatures that I've read may cause neurological damage, or worse. And if you ever need to switch over to paper towel or newspaper substrate (treating for mites or other health concerns, for example), that gradient is eliminated and your safety measure is gone. An unregulated UTH can reach upwards of 120°F and run steadily at these temps. It seems unbelievable, I know, but I do have first-hand data on this. Other individuals have posted similar data here on the forum that you can check out, and I can give you mine too, if you want to see it. I ran my data with both analog and digital thermometers, and I was shocked by how far off the analog was. This could also be true of unprobed thermometers that aren't right on the surface of the substrate or on the bottom surface of the viv, which is where you want to take your temp readings, as these are crucial measurements for your largely surface-dwelling corn. Your UTH may be running hotter than you think it is.
The thermostat handily eliminates this problem.
Many forum members have recommended Hydrofarm thermostats. I will do the same. This thermostat is an economical, reliable choice. If you have the budget, there are even better thermostats out there, like Herpstat, that provide even more precise temperature regulation. However, I've been pretty happy with the little Hydrofarm. You affix its probe to the inside bottom of the viv, next to the thermometer probe over the center of the UTH, with aquarium-grade silicone. (Keep just a touch of space between the two probes.) Once that has cured, you plug the UTH into the thermostat, plug the thermostat into your power source, set the thermostat to 87°F, and that's it. Done. You'll hear periodic quiet clicks as it turns on or off to maintain the 87°F +/- 2°F range.
All you really need to do at this point is keep an eye on the readouts from the thermometer and the thermostat probes over the UTH to make sure they are in agreement. If one or both of the probes gets dislodged by a particularly industrious corn, you will most likely start seeing strange readouts, which will tip you off to the problem. I double-check the probes when I clean, too, to make sure they're still in place and secure on the glass. Additionally, I also double-check all of my readings periodically with a temp gun as a failsafe. (That temp gun:
http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1)
I know you were budgeting for a thermostat in the winter, but I'm hoping that the info I've provided here will convince you to go ahead and get that item now. It really is an important part of your setup. As an additional incentive, it's $5 cheaper than when I purchased mine back on January 4th. In fact, the combo thermometer/hygrometer and temp gun are also cheaper than when I bought them. Bonus! There's always somewhere else that money can go in the snake budget.
I hope this info helps. Good luck, let me know if I can do anything else to help, and above all, enjoy that wonderful snake you have.