Step 1.
Open the Radio and remove everything inside, except for the speakers.

Step 2
Grind off all the excess mouldings off the face plate to allow a flush mounted fascia

Step 3
Cut Laminex sheet to fit the fascia space and cut in the extra holes required for the MP3 player, volume knob and power button

Step 4
Using a 12v mp3 player from ebay as the source of music, it gets mounted up the top
I bought a 15w +15w 8Ohm amplifier to power the speakers. The original amp in the Makita radio is only a 3.5w + 3.5w and the speakers are 10w each. Not sure why they have gone so low with the amplifier.
I also mounted an illuminated power button again from ebay to power the radio on and off.

Its currently running from a 12v power supply from the wall. It powers the button and onced turned on, it sends power to the amp and the radio.

I am waiting for a step down transformer so that I can use the 18V battery from Makita to slip in the back and then drop the voltage to 12v and run the system.