Mains power quality worldwide.

Is there anyone who has sampled power quality in different regions? Is there say a difference in quality between 110V and 240V. My reason for asking is that I see discussions about relatively expensive mains filtering and running dedicated power lines directly from the consumer unit.
Where I live in Cornwall UK it’s 240V 50~ and where I used to live in the Nottingham area. Without any filtering or dedicated power feed, the power is pretty clean, except for a second when the boiler or air con’ kicks in. I can get it really clean with quite modestly priced filtering https://www.amazon.co.uk/gp/product/B00UB0G4DQ/
Turning on other equipment seems to have little effect apart from their initial start up, with the exception of the air con’. If the scope (a friends equipment) is connected to the DC end of the amplifier PS there is very little at all. So am I just very lucky?