It has not been proven that a UV light will do anything for snakes. Most of my snakes burrow and it would not help at all. The only way I can think of that it would help would be with Opheodrys ssp. as they are diurnal insectivores, but even with them, I do not believe anything has been found to indicate it is needed.
I use heat mats for most of snakes, but for some that bask I use lamps (IE the water snake). Andy