Thanks for the links. I just need 4KV now... :P

I am considering running multiple smaller strings already but using 1 long string seems to be more efficient.

Im planning a few projects that will involve having hundreds of LEDs lighting up together. These LEDs use 50mA which adds up to quite a lot and i would probably need multiple transformers to run them all. Running them from the mains would mean theres no need for any transformers so it would be a lot cheaper