If you look at a modern map of Greater London, Croydon is smack in the middle of it, bottom-right-ish. It’s bordered by Lambeth, Sutton, Bromley, and Merton. All London boroughs.
If you drive 15 minutes south from Croydon, you hit Kent. That’s how deep into London-land it is now. The real Surrey starts past Banstead, which is basically where Surrey goes “Keep out, Londoners!”
So, geographically, Croydon is part of London’s urban sprawl. The M25, the concrete, the 24-hour chicken shops—it’s all there. Surrey villages have duck ponds and cricket greens; Croydon has a tram system and a statue of a walking robot.