I did this the other day on my
cupra! It is a right bitch to get that end cap off, I firstly cut off about and inch and a quarter in length first (with a hacksaw cos of the metel bit inside) then with the cut off piece, I ripped out the rubber with the
help of a small screwdriver, then eventually snapped the 2 metal prongs out, this was very tricky althought it looks like there is a plastic clip holding the metal pieces in place and if you force a small flat head screwdriver parallel along the top, into the cap, this should release the metal prongs. When you have the plasctic clip you'll notice that the remaining blade is slightly wider than the plasctic end, this is good tho because if you just press the plastic cap back on the end it will secure itself with a tight fit and stay on there with no other work needed!
Sorry if this is a bit confusing but hard to explain! Don't be afraid to play with it, it will probably need some force to get the clip off, its pretty tough, just be careful you don't brake it!
HTH