Got a few more things sorted.
Had to remove the bumper, passenger side skirt and fender for two reasons. First, the passenger fender needed re-aligning as it was clipping the door slightly. Second, the Active Steering module on my car was also causing issues and blocked the fender badges from clipping in fully.
Relocated and secured the module with some zip ties and double sided tape, and got the troublesome fender aligned properly this time. Plenty of room for the module to sit tucked away and for the fender badges to be fitted later (surprising that the module is about the same size as the DME!)
Then moved on to swapping the original bonnet for the M3 item. The M3 one is a good 5-10kg lighter than non-M, as it's made of aluminium and not steel.
Started mocking things up and realised a few things needed fixing, so off came the bumper again to make sure headlights were all lining up and bolted properly. Then onto aligning the bonnet enough so it'd close and not smash the windscreen on the way to the shop.
Great success!
Starting to see the light at the end of this tunnel. Just need to put the new front liners and ducts in, extend the wires for the ambient temperature sensor and modify the M3 belly pan to bolt up to a non-M front subframe.
Will also need to give it a quick wash and swap the stock wheels over, after which I'll be taking the car in for chopping up and prep of the rear quarters.
This has been a pretty high effort all things considered, but will hopefully be worth it in the end. Nice to know that I've shaved about 20 odd kg's with all these M3 bits so far. Definitely need an aftermarket exhaust to shave some more haha.