Extend the Story - Add a Room

"Excuse me!" you call out, cringing at how upper-class you sound. The teenagers, guitars slung over their shoulders, glance over and spot you.
"Excuse me!" you call again, to catch their attention.
"Yeah mate, what?" one of them asks.
"I'm..." you falter. "I'm looking for John Lennon?"
The kids exchange shifty glances.
One with a duck's arse hairstyle pipes up.
"Oh, yeah, who's askin'?"
You hesitate. You can't risk saying a fan.
"A friend of his."
One of the boys, who is smoking (and looks far too young for it, until you remember it's 1957 and you can smoke at 16 these days), blows his smoke into your face.
"You look a bit old to be a mate of his."
"Well," you say. "I am."

They stare at you for a little while, until a boy approaches them. His hair is in a quiff. He has a guitar in one hand and a bottle of beer in the other.
"What are you wankers talkin' about?"
He is unmistakably John Lennon.

"This guy says he's a mate of yours."
"Oh, does he?" John swaggers. "What do you want, mate?"

You have to think quickly. How do you explain this one?

I'm a time traveller from 75 years in the future and a massive fan!