i've stripped my hair from black (using colour b4 extra strength you can get from boots) and it went like so:
my natural hair colour is ginger anyway, so it came out pretty sweet and it DIDN'T damage my hair noticably. obviously it does damage yr hair, but yr not gonna be walking round with like straw hair.
since then however, i've bleached over it time and time again. and the more and more you bleach it the less and less stripper will be able to take it back to yr normal colour. the colourb4 website and reviews online are really interesting :)