In Scotland they won’t say what the leeway is, but it is typically 10% +1, much the same as elsewhere. This includes the average speed cameras on the A90.
Of course, the authorities can change this at will and mobile speed vans can be less forgiving, run as they are by the local councils as revenue generators.
Moot for me now as an EV is thirstier than a dehydrated camel once you are over 70. Bad enough to have me looking with sadness at the demise of all the decent diesels on the scheme…
In life, it's not who you know that's important, it's how your wife found out.