Finally got round to adding the JB Speed M4 style spoiler to my M240.
After watching this video:
I used a hair dryer as I dont have a heat gun and took my time heating up the OEM spoiler (and the subsequent adhesive - what a PITA that was).
Any how, the spoiler from JB Speed fit perfect and looks exactly how I wanted. I added a few lines of 3M tape so I hope it stays in place!