[MiNiGuY]

The spoiler is attached to the top of the tailgate using double sided pressure sensitive adhesive tape. It is then bolted with 3 10mm bolts from the underside of the tailgate.
The plastic plugs you can see when you open the tailgate are the covers for the bolts.
Removal is simply a matter of removing the plugs and removing the 3 10mm bolts.
Best way to remove the plugs is to force a small flat blade screwdriver through the side of the middle portion of the plug and lever it off. The holes will be unnoticable and the plugs stay in good shape. Trying to prise them off from the outside edge will scratch the paint and leave the plugs looking like they've been chewed by a Rotweiler.
Next the spoiler has to be forced off of the tailgate by pushing until the tape gives in and lets go.
That's it, but easier said than done. Not enough force and the spoiler refuses to budge. Too much force and you risk bending the top edge of the tailgate. It's a very real risk too. don't under estimate the situation.
Take lots of time and build the force up trying sharp pushes and always checking for the slightest sign of movement to the tailgates top edge.
You will not believe how strong double sided tape can be!!
The back wheels will be virtually in the air by the time that bugger gives in!!
The bolt threads on the spoiler will cause slight damage to the holes in the tailgate. This is unavoidable but obviously you're gonna fill the holes or cover them with another (or the original) spoiler anyway.
Don't try cheating by forcing instruments between spoiler and tailgate. The paintwork will never forgive you.
If you use adhesive of any type when replacing a spoiler be sure it is centered correctly on the tailgate before allowing the two to contact.
For cooper S it's the same principle but only two bolts, and the risk of tailgate top edge bending is significantly increased due to the shape of the spoiler. I find on these that if you can free up one side you can lever the spoiler and twist the other side off.