Welcome to the forum!

I have to congratulate you on doing the research and making changes to accomodate your new pets.

You're right in assuming that the UTHs are the way to go. The exo-therm heating pads should be fine. If you want to upgrade, you can take a look at some of the UTHs on Beanfarm.

You can certainly get by with a dimmer especially if your home temps stay pretty steady, but it's always nice to have the security of a thermostat. I know a $100 thermostat might seem like a lot of money, but if you think about the number of years that you'll have your snakes it really isn't that much.

Good luck, and try to snap some pics if you get a chance!