Hi All
Well it's done and I'm very happy apart from a couple of issues; one fairly big and one not so.
In the end I decided to do it as easily as possible, and to leave eveything stock so I could reverse it if required.
I bought a couple of ISO kits from Maplins (so I could chop and change if I wanted) and I used the original ISO plug in the loom to supply constant power, and ran a new connection from the fuse box to source switched power to the device. This was the one slight headache as the unit I bought doesn't seem to have a complete "Off", it just seems to stop outputting sound and turns off the display but leaving all the lights on like a Christmas tree (not ideal in a rag top), if I could have turned it off completely I might just have wired them both to permanent live. I also just rewired the speakers using some new cable and a few spade ends, again so I could just unclip the original wiring and leave it in place in case I wanted to put it back.
I haven't used it much yet but so far I've been surprised by a couple of things. What's good: Absolutely love the Pioneer, much better sound even using just the the stock speakers in the dash, not even wired up the door sub. I love the fact I jump in the car, turn on the ignition, iPhone and unit connect automatically using Bluetooth, unit starts the music app on the iPhone and starts playing the track where it left off last time, I don't even have to take it out of my pocket :clapping:
Another thing is the Satnav on my phone (I have Navfree, I can't endorse the app as I've not used it much, but it's there if I need it), I start the app on my phone and when the nice lady has to tell me what to do, my music volume lowers and I get "Turn right at the next junction" or whatever direction I need...who needs TomTom?
I read there was a additional cable you could buy to hook up the iPhone if you need more facilities than the Bluetooth but I didn't bother. I did want to see if the USB would charge the phone though so hooked it up and it does, I think. The reason I say I think is because I forgot to look, as soon as I connected it I noticed USB source had control over the iPhone...I could use the unit to scroll through my music, album artwork came up on the display, what extra's the cable gives you I don't know.
The only really bad thing is I can't get a radio signal using the Fakra connection in the Porsche. I bought an adaptor (Google PC5-111) and hooked it up to the black Fakra connector but didn't get any signal to the unit. I then tried an amplified version (PC5-137) connecting the blue cable to the blue cable coming from the ISO (connected to the white cable on the original Porsche loom) which I believe is the powered antenna control, this might be where I've gone wrong and would be appreciative of any correction. The other slight issue which I actually thought I'd have to rectify anyway is the slightest of gaps around the facia, maybe a couple mm and can only be seen when you get down to the same level as the unit, I think I'll probably live with it.
Thanks to all that helped me and if anyone else stumbles across this please don't hesitate to get in touch if you think I can help.
Smeg
PS: Anyone want to buy a PCM 2 unit with Sat Nav? :)