Ruth, I haven't seen this before but like the idea of it - recycled loo roll of course
The soap in the link is one of those soaps that absorbs loads of water and goes to mush if it is exposed for any amount of time, it also contains loads of moisturiser and i am not sure if these particular properties are crucial for this activity to work or not?
A more natural soap to try, and one that also absorbs water and can turn to mush if not left to dry is Oliva olive oil soap which is: kind and gentle to the skin; not tested on animals, contains no artificial colours or perfumes, is vegetarian, 100% biodegradable and contains saponified olive oil, water and mineral salts.
I am not sure that it would offer the same results though and so you would have to try it first - it is 79p a bar.
anne