Geomog,
You don't need a wiring diagram The factory have made it simple ---I have a 2009 Plus 4 and have installed a radio. Even though you may not have a radio prep kit, I can assure you that the wiring is already there. Behind the blanking plate you will find the DIN plugs which go either directly into the radio or into the harness which comes with the radio. You will also "Feel" the holes for the speakers behind the carpet just in front of each door -- the aluminium mounting plates for the speakers are in every car and you'll find the speaker wires there too! Check behind the blanking plate on the front of the heater box and if the two din plugs are there then the speaker wires are installed too!
If you cut the hole in the carpet revealing the speaker wires, you can drill a hole for the aerial from the inside thus saving you measuring etc on the outside -- use a small dia. drill so you can expand the hole size from the outside to the size required to get the aerial wire in. Halfords stock the aerial -- about £20. I used 5in VDO speakers, The wires in the car just plug in - mount them with the self tappers included with the speakers.
Mounting the radio is a doddle - you just remove the tabs which the blanking plate screws into and insert the DIN carcass(comes with the radio) into the opening - I actually fixed it in using stick on velcro top and bottom, but you can bend the various tabs as the radio installation guides say - I think that is a bit fiddly! Connect the DIN wiring as in the installation guides - it just plugs in and push in the radio set ---Done
I use a Sony radio and a steering wheel remote from a company called Auto Caress(just google them) which costs £15!!
I have a spare Sony BT2700 radio if you are interested - PM me and we can reach a deal!.
Cheers
