Met Cilla on the set of Corrie years ago when I was a joiner. She was a royal PIA then, about 1983. No change it seems in all that time.
In a new life, I met Celine Dion and Madonna (a day or two before her wedding) on separate occasions and they have provided tons of great anecdotes because of their terrible attitudes.
By far the best celeb was a tennis player from US, Jim Courier.
All the rest were well behaved, ie didn't appear on my radar.