Update to 12.29 Not Working (MAC)

[hm279]

Hi i was wondering if anyone can help me out:

I've been running 0.12 and this morning on launch factorio offered to update so i click yes and the game crashed with an error message, thinking it may just need a relaunch, i relaunched but the same message kept coming up, so i tried deleting the app and reinstalling from the website- which after i unzipped the .dmg gave me an error message telling me unmount the disk.
What ever i try it wont allow factorio to run, so i tried loading the old .dmg from 0.11.8 and updating from there, however that also gave me this error: (Imaged & Below)

boost::filesystem::remove: Read-only file system: "/Volumes/factorio/factorio.app/Contents/data/changelog.txt"

Please does anyone know whats going on/how to fix?

(Running on 2012 macbook pro OS X El Capitan, 2.5 GHz Intel Core i5 processor, Memory: 4 GB 1600 MHz DDR3, Graphics: Intel HD Graphics 4000 1536 MB)