Ok here we go then.
First job is obviously ripping the dash open. Very easy to do in the Mazda.
Before you start, remove any bluetooth pairings you may have (if you have factory bluetooth).
1. Remove the handbrake trim. It's only clipped in, you can put your fingers under the trim by the handbrake lever and also the other side of the cup holders. Tug hard and it'll come out.
2. Unscrew the gearknob and pop off trim surrounding it. Again only clipped in.
3. Starting at the bottom (nearest the gearstick) take off both shiney trim sides, open the glovebox to assist the passenger side trim.
4. Now take off the trim surrounding the air con controls and gear stick.
5. Remove the 4 screws holding the air con controls in place, pull the controls forward and disconnect the plugs (there are 2).
6. Remove the air vent/speaker grill. This is the hard part, it's difficult to get off. Protect the trim using tape and gently lever out with a flat blade screwdriver. Once out, disconnect all plugs and put aside.
7. Now there are 2 screws at the top of the stereo and 1 screw and a bolt at the bottom. Remove all these and the stereo will pull out, disconnect both plugs.
So now the radio is out and all trim removed ready for install.
First things first, the GPS antenna. I found a lovely location right in the top of the dash but hidden from view. If you look at the speaker top panel, either side of the speaker there are two holes. One is take up by some kind of sensor, the other is empty. The GPS antenna that came with the F900 fits in it perfectly, nice and tight. Pic below :

Next the Mic. The pioneer bracket is a huge piece of ****. So I did away with that and stuck it up by the lights. Not 100% happy but it'll work for the time being. I might try a new Parrot mic to see if that works.

Now you need to replace the top display (mazda part no. GS1DV7010) , well I think you do. The replacement I got from Mazda looks identical, but I think it controls the Trip computer differently. So swap that out, only 2 screws hold it in place. When it's in you can install the adaptor cable, (Mazda part no. GS1DV6609). This effectively goes inline with the existing plug and has a long single wire that goes to the steering wheel.

With the adaptor and antenna in place you can reconnect the other plugs and rest the trim back on top, do not click it back in place.
Next the stereo. As said before, the cage and stereo trim surround that came with the Pioneer is junk. Remove it all. Now order the following fascia adaptor, ebay number 400028650732 and the double din chassis 400026615808. You must use these 2 together to fit the pioneer. Now the chassis comes with 2 different sets of locking plates (these bolt on the side of the radio and click into the din chassis. You can vary the depth of the radio depending which you use and which holes on the radio you bolt them to. My first attempt had the radio set far too far back so I changed it and it's spot on.

Now you can get it in, plug the loom in first into the factory loom, FM antenna fits straight in, no adaptor required. Plug in the power loom to the radio, then the preout loom. Connect mic and gps antenna and switch on ignition. Now assuming the loom is wired correctly you will have no problems, all colours are like for like so mistakes should be minimal.
Tape up any unused wires and feed the USB and Ipod AV cables behind the dash down under the gear lever.
Once the radio is powered up, you can set up the PAC steering controller. It's VERY easy as long as you follow the instructions.

I couldnt find this in the UK, but ordered one from ebay and it came from the US in a week. Just search ebay for PAC SWI-PS.
With that programmed and tested you can tidy up the wires and put the stereo in. The stereo trim sits behind the top trim so lift that out of the way if needed. Once it's in, test all radio functions, GPS signal, FM and ipod. For the ipod you will need to enable Aux1 in audio settings to ipod otherwise you will have no audio.
If everything is working, clip the top trim back in (this holds the top of the radio in place securely. Next refit the air con controls, trim and such reversing what you did at the start.
The sound stock is very heavy on the bass but otherwise superb ( you can turn this down of course). The Bose amp and speakers do an excellent job with the Pioneer.
The finished dash :
