So it was a toss up between a Chinese made unit such as Dynavin/Andrive or a double din unit by a reputable manufacturer. I went with the latter.
I didnt like the look of double din fitting kits you can get and I think is the normal route to take. I think the plastic finish destroys the interior and takes away the good looks that a double din unit can have.
So with the help of Sanj (who else!) we (he) examined the dash. Pulling the old unit out was an issue as it had a brain box, blue tooth box, a DVB box AND a bloody ipod box all stuffed behind the glove box!
The picture below shows the approx cut lines. Ignore the red lines as I took this pic off the net. My cut lines were done in yellow. It was a pain but with Sanj's typical Indian tool box the job was done.
Since I already had a single dine fitment, this was an advantage in what I wanted to do as the unit fit like a glove and i didnt need the additional bezel brackets that would normally be used.
Once the dash was cut the unit went it. It was extremely snug but it works perfectly, makes it harder to nick and there are no rattles or shakes.
Next step was the surround. Sanj quite rightly highlighted that the surround was the most important part of the install. I got the idea for the surround from the install that already came with the car.
The surround above was made with some timber and padded up and convered in leather that matched the seats.
I took the measurements of the surround and asked the local timber yard to cut it up for me. I smoothed it out and added the curve to blend in with the dash as much as possible. I left about 5mm of a gap at the top which allows for me to stick a knife or screw driver in should I need to take the fascia off. Total cost was £20 for timber and cutting.
Im happy with the finish, Iv currently got the iPod cable in the glove although this will be replaced in the ashtray most likely.
The double din unit itself is a Pioner AVH-4400BT, its got the features I need, and the sound quality is a huge improvement. The radio isnt working at the moment but this will be further explored in time.
Alot of people have commented how "lost" double din units look in an X5 but in reality it looks really good and i think Sanj agrees too.
Big shout out to Pa Ji Sanj for helping out!
Never anthropomorphise computers. They hate that.