Citroen xsara picasso radio wont switch on?

Im having some trouble with the radio in my S reg picasso. for some reason it isn't switching on. I hear it trying to read the cd but none of the buttons respond and i don't get anything on the cars display.

I noticed when driving the car at night that the illumination around the radios buttons was a bit intermittent. I tried giving the radio a bit of a nudge and this caused the lights on it to go out, giving it another nudge made them come back on e.t.c i assumed it was a loose connection but i took it out today and unplugged it and plugged it back in and all the connections seem fine.

I also tried disconnecting the cars battery for half an hour then re-connecting it to see if that helped but it doesn't seem to have made any difference.