I'm not sure if the following account is about the same Peter Grant who was Led Zeppelin's manager or not.
The places don't seem to match up; I didn't see Hull mentioned in the wikipedia account, but the timeline makes sense as he would have been 5 years old in 1940.
Bombs fell in London in 1940 so that part matches.
This is the first I have read about this story from the BBC archive of WW2 memories; wow, the following account may be from someone who knew him when he was a kid.
Or, it may have been a different Peter Grant, as there is a substantial distance between Grayshott and Hull. However, it makes sense that he may have been evacuated from Grayshott to Hull and then to Scotland.
Led Zeppelin's future manager, Peter Grant, was a boy of four years old when Britain began to evacuate its population to safety.
John Bonham, John Paul Jones, Jimmy Page and Robert Plant were all either too young to remember the evacuation or born afterwards, but Peter Grant was old enough to recall living through the event himself.