Just to add a couple of points to this.
Firstly, the pins on the connector and switch may not line up perfectly. If that's the case DON'T FORCE IT! When it's line up it slots in with very little effort. If you push the plug in and it doesn't slot straight home, check the end of the plug for witness marks where the pins have touched it and use a small screwdriver to VERY GENTLY move the pins slightly to align them.
Secondly, the cowling. As can be seen in many of the pictures, the line in the moulding on the cowling is pretty much spot on for width so you can cut up to the line with no issue. The line across the bottom is different. I've found there is a fair bit of movement in my cowling when it is fixed in place. It's enough to change it from OEM fit to a retrofit finish. I'd advise to cut 5mm above the line and trial fit it around the switch. Then use a file to gradually open up the slot until you get a good fit. I cut to the line and have a small gap. If it goes totally Pete Tong a replacement cowling is a tenner on ebay. The factory cut cowlings do come up but they're rare.
Finally, current price of the switch from the stealer was about £110.