Earlier quoted context omitted.
Australia by and large is also much less grubby than the UK. (I say, 'grubby' not 'dirty', because I don't know whether the UK is actually dirty. Eg all the buildings just look dirty and drab compared to Australia. Perhaps it's a leftover from centuries of burning lots of coal?)
I agree, Perth has always seemed sparkling clean compared to most cities in the UK. Other Australian cities I've visited seemed that way as well. I think partly it's the light - it's so bright here in Aus that things look cleaner anyway, but also the light and the heat keep things a little cleaner, UV sterilises and the sun bleaches after all. Aus doesn't have as much of a legacy of concrete brutalism, either, lumpen…
You are right about the smell of urine and pot in London.