I have a product that i use for soft washing of listed buildings. Mix at 50:1 spray and walk away. Covers about 4/5 sqm per litre of mix depending on porosity of substrate . Algae and moss die within 12 hours and the cleaning takes place at is own rate over 3/4 months by the wind and rain...very gentle but also very effective.
£20 is not too expensive but I'm not prepared to pay out for a product that just you alone says it works.Then a kleeneze gag is thrown in, which in my mind cast doubt, especially when someone like Blastaway (Lee I think) is saying it. Having met Blastaway and read his posts, i would be trusting his views first.