I used a jet/pressure washer Monday morning to clean some patio furniture that were is desperate need of cleaning. I'd already tried scrubbing them, using chemicals, using magic sponges and everything else I'd read inline. They didn't work. These chairs and table had been outside for years without a full wash.
An hour and half with a pressure washer and they look like new - yes, they are noisy.
I chose mid morning to lunch time as the time to do it as thought people would be more likely to use their gardens for lunch, afternoon and evening. I also deliberately didn't use the weekend as people are more likely to be outdoors, so I did consider other people and when they were more likely to want to be outside enjoying their gardens.
By the way - anyone with 'Astroturf' or artificial grass (they are different products) - don't use a pressure washer in them. It will wash away the sand and other stuff used underneath the grass and cause potential damage. It's one of the things you're told about.
As for 'elbow grease' - I tried that and it didn't work. Plus the elbow grease makes my arthritis in my elbow very painful. The pressure washer did a bit but not to the same extent.
And the 'car chaps down the round for a fiver' - probably still using some for of jet wash for parts of the car wash, also known to encourage modern day slavery, and the chaps are probably not even taking home minimum wage. It'd cost a lot more than a fiver to avoid some of those pitfalls from such outlets.