I'll not tell anyone on here exactly how to get the old headunit out (security and all that), but if you need to know i can aid you. It is quite easy to do, just need the right tools.

So In this article i'll show you how to get from the factory fitted HU to the one of your choice (normal single din sized tho!)

WARNING: make sure you have the code for the old radio BEFORE you remove it or disconnect the battery, as it'll cost upwards of £20 to obtain it afterwards!

You will need:
Wiring harness for your HU and adaptor harness to Vauxhall wiring
New Head Unit (inc cage)
Replacement Fascia
Flatblade screwdriver
Torx T15 security bit
Cutters
And some time (how much depends on the installer tho )

First, once the old HU is out you'll notice a metal frame inside the hole tats left, this has got to go!



There is a T15 Torx screw at the back holding the thing in:



With the screw removed, you need to bend all four edges of the frame inwards to "unclip" it from the dash:



Keep pulling and gently bending the edges and it'll eventually come out.

Once its out you then need to remove the aerial and multipin harnesses on the back, these simply unclip







You should be left with something like this:



Adding the additional wiring harness (Autoleads PC99-X06 stalk control adaptor with HU specific patch lead) i found the extra connectors are too fat for the gap on the vauxhall one.



So, what you need to do is remove the yellow plastic clip, then seperate the three blocks.I found using a wide flatblade screwdriver and a pair of cutters made light work of this.
Just be careful not to damage anything!





One free,now the others!



Now as the song goes....plug in baby! Make sure you line the right conectors up! the power wires are the thicker ones, and on the adaptor it should say which is which, just get it right!
Now would also be a good time to test the HU and your wiring (re-connect the battery!)

Assuming all is well, the replacement fascia can be fitted (in this case Autoleads FP-19-00) which clips straight in, may need a little gentle persuasion!



Fit the security cage, and bend some of the lugs out to secure it properly, be careful not to pinch any of the wiring as it can cause a fire if it gets shorted out.



Finally you can plug the antenna adaptor inif needed and connect the whole lot!



Incase you want to know the HU is a Mutant MT1105USB, MP3 CD/CDR/CDRW player with line in, SD card slot and USB port. Really decent little unit!

did you have to swap the live wires around to keep the memory, I had to when I fitted a goodmans to my old corsa C, same when I fitted panasonic into current astra.

something about constant live and ignition live.

Yes the 12V memory and ignition are the wrong way round, but it's easily sorted with some bullet connectors. Forgot about that!