Hello :rasp:
Yeah, I have a DVD headunit in my car.
The above headunit looks like this outside of the car:
The Head Unit space is a standard single DIN slot. If you can get a shorter head unit (in terms of how far it goes back into the dash), it will make things easier for you.
Now it's a fairly difficult job to fit it all in. The GPS unit and bluetooth units are mounted in the passenger footwell and behind the headlight adjuster panel respectively. To fit it all in, I put the external boxes in first, ran the cables into the radio space and hung them out for the time being. I tried to take as much of the cabling as possible down behind the heater control panel (this is a Phase 1 remember), and when I had wired everything in, I connected it all to the back of the head unit, and reached up the back of the heater panel and pulled all the wiring down as I slowly fed the head unit in. It's seriously tight and if your headunit it particularly long the last inch or so is REALLY hard to get.
So yeah, all I can say is try and pull all the cabling down underneath the stereo into the space behind the heater panel, because there isn't any room behind the stereo. IIRC I was actually able to move the cable connector to the side, but it was still tight.
Oh and if you have a GPS unit too you'll have to run antennas up to the roof, and with the bluetooth unit a microphone had to go up to the roof too.
It's fecking hard, you'll swear, you'll probably pop a fuse at some point, you'll cut your hand open on the cage and you'll probably come close to giving it up. But if you keep at it, and manage it it's feckin' cool.