BCM4306, b43 legacy driver installed, but "firmware missing" error

_{converted comments as answer}

To ensure that wireless works correctly with the BCM4306 wireless device try the following:

1. Remove the b43-legacy package you have installed.
2. Connect your laptop with a wired connection and test your internet connection works.
3. Search in Dash for Additional Drivers and it should open a window and offer you to install the b43-cutter - activate this.
4. If the above doesnt work, then the missing firmware can be found by installing the following package:

sudo apt-get install firmware-b43-installer

I followed this guy's steps, except the last two lines were in /lib/firmware/, not in modules.

EDIT:

Above as a small shell script, for easy cut and paste.

#!/bin/bash

set -o errexit
set -o xtrace

TMPDIR=$(mktemp -d)

cd "${TMPDIR}"

wget "http://downloads.openwrt.org/sources/wl_apsta-3.130.20.0.o"
wget "http://mirror2.openwrt.org/sources/broadcom-wl-4.150.10.5.tar.bz2"
tar xfvj "broadcom-wl-4.150.10.5.tar.bz2"
sudo b43-fwcutter -w "/lib/firmware" "wl_apsta-3.130.20.0.o"
sudo b43-fwcutter --unsupported -w "/lib/firmware" "broadcom-wl-4.150.10.5/driver/wl_apsta_mimo.o"
sudo chmod 775 "/lib/firmware/b43"
sudo chmod 775 "/lib/firmware/b43legacy"

cd -
rm -r "${TMPDIR}"