Ctfr all the way, I get it from Suffolk Chemicals in Hadleigh, about 35 quid for 25 litres, lasts ages, water down, but not to the 1:1000 suggested I tend to do anything from 1:30 to 1 to 100 eats through grime wonderfully.
Did a sloping roof with just pure the other day. Should of been 15 minutes with Ctfr, took an hour with just pure water! Would of been quicker to come home to get the sprayer!