Fake iPhone 8 or Genuine ?

The printing on the back of the iPhones varies from country to country it was manufactured for. I would be concerned if you got a supposed brand new iPhone which did not come in the original box. Ebay sellers are known for not selling what they claim.

Check the model number in Settings > General > About > Model. If it was new originally, the model number begins with M. If it's refurbished it begins with F or N.

No eBay seller is selling truly new (I.e. never sold at retail) Apple devices since no eBay sellers are Apple Authorized sellers. So strike one to the seller for claiming any iPhine they sell is “new”. It may be un-used yet, but it is not a retail new device since no eBay seller has legitimate, legal access to Apple wholesale supply.

And yes, any legitimate and truly new, or purchased legitimately from Apple or an Apple Authorized Seller but never opened and used iPhone would be an Apple iPhone box, with headphones, wall adapter and lightening to usb cable, plus documentation and a sheet of Apple stickers.

The only devices Apple ships in plain boxes are service replacement units.

So I have no idea just what you got, but what you did get was not what was advertised - that much is clear.

If you're happy with it and it meets your needs, then keep it. But be advised, your iPhone has NO warranty in the UK. If you have any issues with the phone, you'll be flying to China for service.

Me personally, I'd return the phone and buy one in the UK where it's absolutely new and comes with a warranty valid in the UK.

Edit: Apple does not replace the backs of iPhone. The back glass is fused on and requires a total replacement. If there are marks on the camera, you did NOT get a new iPhone. Whether you keep what you got is up to you. It would be boxed up and on its way back to the seller if I bought it. But then I only buy from Apple directly to ensure I don't ever get scammed.

Who is that 18 month warranty from? Your screen shot shows it clearly was not a new device. It was sold to someone somewhere else initially, which is why the tech support has expired since the Apple warranty starts the day of retail sale by Apple or an Apple Authorized seller.

Not all models have the “Designed by Apple ....... “ on the back. To determine the authenticity, enter the serial number at checkcoverage.apple.com

I guess this is why I never use eBay. A seller who falsely claims to be selling new devices is not a business I would have any confidence in keeping their word about anything they claim.

Exactly. I would have ZERO confidence in anything this seller says. The old saying "buyer beware" is so true with eBay.

That's up to you.