im so happy to read you're more concerned with safety than price. TBH a reliable thermostat protects you and your home as well as the snake; a runaway heating element for pets is a common cause of house fires.
you will need a second thermostat with your house conditions. i stared out using Jumpstart thermostats, and i still have them for backups; one quarantine enclosure of mine still uses one. now i use expensive yet reliable Herpstats (Herpstat 2 and a few Herpstat intro+) and i have one VE300 (Vivarium Electronics). the thing that sucks about the cheaper thermostats is that they run and either 100% or 0% with no inbetween. for a cheap electronic control, over time this will easily cause the unit to fail, and since our snakes live 20+ years, this is not ideal.
i used a Jumpstart for almost 3 years without fail, but i would NOT take the risk of assuming it won't fail on you. i consider Jumpstarts an economical bridge between now and the time it takes to throw that money down on a reliable thermostat (Herpstats).
i hope this helped! you do need an ambient heat source. lmk if this was confusing or if you're having issues getting another electronic control.