I found the project by Francis Baines you mention. It is certainly interesting, but only seems aimed at estimating how much UV reptiles and amphibians are exposed to naturally, and how to replicate that exposure in captivity. I don't see that it makes any attempt to establish the value of such exposure for rodent eating snakes, and it even warns of issues that exposure can cause, such as skin cancer and vision damage. I only skimmed it briefly though, I will have to read it more carefully when I have more time.
The link for those interested:
How much UVB does my reptile need? The UV-Tool, a guide to the selection of UV lighting for reptiles and amphibians in captivity.