I would agree with gramps. I have a genuine grip on a d750 (purchased second hand) and a Meike grip on a d7200 (came free with the second camera), there is definitely a difference in the build quality between the two, the materials are much better on the Nikon grip especially the buttons. The connection on the Nikon grip is better, the Meike camera connection socket sticks when removing the grip and the screw just doesn't feel as secure. There is also a little movement between the grip and camera. If you hadn't had a genuine Nikon grip before it would be harder to notice these differences as they are quite good copies but I doubt they are from the same factory like someone have said they are.Having had both there is definitely a difference between Nikon OEM and Meike, though whether it is £xxx difference is highly questionable.
I did also have a Meike one for my original D810 and it was faulty and went back to Amazon for a refund.
You did well, for that price it's definitely worth it.I certainly wouldn't have paid for a brand new one at £200+. But for £100 I couldn't say no, especially the build differences in all the reviews I've seen between OEM and aftermarket. The magnesium body of the Nikon grip is gotta be worth having if the price is right.