This article from last years agrees that the frequency of cleaning UK city buildings is quite low. https://news.ycombinator.com/item?id=17883481 https://news.y

This article from last years agrees that the frequency of cleaning UK city buildings is quite low. https://news.ycombinator.com/item?id=17883481 https://news.ycombinator.com/item?id=17883481 https://www.manchestereveningnews.co.uk/incoming/gallery/blackened-buildings-manchester-before-clean-8727918 https://www.manchestereveningnews.co.uk/incoming/gallery/bla... I also stumbled upon this discussion on cleaning London buildings in a Lords sitting in 1964 which was quite fun to read. https://api.parliament.uk/historic-hansard/lords/1964/nov/12/cleaning-of-londons-public-buildings https://api.parliament.uk/historic-hansard/lords/1964/nov/12...