The ultratherm UTH from scotland are very safe heating units. they are designed not to get as hot as most. In a normal room temp of 68ºF (20ºC) they typically do not get hotter than 90-95ºF. In very cool rooms with heavy bottom enclosures they often do not get warm enough to generate correct temps. Ultimately the internally regulated heaters (like ultratherm and kane) are much safer than the typical UTH. Contrary to what some say, a is NOT thermostat is optional with ANY UTH.

The hydrofarms are a but squirley, they do not have accurate readouts (4ºC error range •that is 8ºF•) additionally they allow 3º under before turning on and 2º over this is called swing. They other quirk is the probe it is metal and heavy, with slow responding electronics. This means it is slower to react to changing temps. They under the exact wrong conditions (cool room plastic tub and powerful heaters like flexwatt 4-11 inch) can produce temp spikes that are quite dramatic. The seem to do best with lower power heaters and thicker bottom containers. Understanding the limitations of any product will increase the margin for safety.

I too have adopted an old snake as well I have had him for 2.5 years now. He lived in his second home for 16 years or so and arrived there as an adult. They can be exceptionally imprinted both on food and enclosure. My advise is you have already made a massive change to a new location I would keep the snake exactly the same as he has lived for 15 years before making another change. Get him feeding well (10 or more successive meals) before attempting a enclosure change. Clearly he is well adjusted to the enclosure he is in currently as he has been in it for a long time. I made the mistake of switching my old man when he moved to a new enclosure. He refused feeding for 11 months the temps were corrected 80-90 (over the 75-88 he had originally) and he went into a rack from a tank. After 11 months of trying everything (including buying frozen rodents from the same original supplier 100 km away) I decided to return him to is tank with his stuff he had when he arrived. I dropped is temps to 77-89º and a week later he broke his fast and has not refused since. They do not always adapt to new things easily or well. Look at the problems switching an adult mouser to rats it can be difficult. Smaller snakes are a different thing they adapt well but older ones especially ones that very very very likely are wild caught (15 years ago this is highly likely) I would proceed very slowly and not make big changes quickly you may seriously stress the snake.