Headunit not responding

[AlecShort]

Hi folks.
I have a 2001 4.4 sport with a weird problem that started today. Car started up, CD player switched on with a nice bit of volume. Pull up at the petrol station, press the off button on the headunit and nothing. Try to change the mode to radio and stuff, display changes but still plays CD. Can't turn volume down, can't turn it off and when switching car off it is still playing. Oddly enough I can change CD but that is about it.

In the end I have taken out a couple of the fuses from the boot (72 & 73). Anyone got any thoughts on why my headunit is all of a sudden playing up? It is the one with cassette player built in and CD changer in boot.

Thanks for any help you can offer!
Alec