On a budget? Just use 500, 1000, 1500, or 2000 grit sandpaper to smooth it off and cover the doors with BMW stripe M decals.
For around £200-£250, which includes an electric pressure paint gun that connects to the wall outlet, you could spray wrap the entire thing if you're comfortable with that kind of thing. I get my spray wrap paint from a business called Matt-Pack, by the way.
Go ahead and search "DIP YOUR CAR" on YouTube if you're feeling adventurous and want to see some spray wrapping.
Spray wrapping is a relatively easy technique that I've been doing for a few years now. Once you have the equipment and are skilled at it, your friends will want you to change the colour of their motor.