Interesting chris, never heard of that law.
Ive found fairy is just right for render cleaning and cladding. Granted I haven't tried clever wash etc.
If fairy is safe, and works well, no need to buy from the likes of Benz/softwashuk!
I've just completed a roof clean for a building company. Scaffolding was up which made it easier.
But here's the surprising part - before I had even quoted I was amazed to see the site manager had a clip board and a method of cleaning from the architects. And guess what they recommended:
'A bleach solution mixed with water and soap to clean the roof of algae and lichen'
I said to the site manager 'I've never been to a job where the company themselves know what to use'
Anyway, that's exactly what I did, and it came up well.
I went up to see Ben at Rutland pumps and he sorted me one of his new roller pump machines, works a treat.