After using numerous patio/ Drive cleaners, I used a product called moss- go, There is a regular one and one for algae and stains, The Latter suited me, I used 1 part moss-go to 5 parts water in a watering can and applied, Thoroughly sweep the area first though, Let it soak in for 48 hours and wash down, You need to do this only when we are expecting 48 hours without rain, It costs around 30.00 euro but you get what you pay for, You can get it in woodies, Patio looks great now so off to buy a sealer at last.