Ok so what did I decide, just incase it helps someone else.
I am well aware my decisions were based on others recommendations, comments, not first hand experience and added to my preferences.
Head Unit - After reading the forum posts and speaking to a couple of installers I have decide to go with the Discover Media Sat Nav together with the App Connect & Media Control option. Both the Kenwood 516 & the Pioneer AVIC will mostly be compatible with the Multi Function Steering Wheel (MFSW) and the Multi Function Display (MFD).
However for me I will only get annoyed with functions that are not 100%
I was told that the Pioneer & the correct interface modules would work with the MFSW but not work with voice control (wouldn't use that anyway) and that the MFD would work mostly but tends to not always update. The pioneer also would not be able to display the parking sensors and the rear view camera on the same screen, just choose one or the other in the setup. Not really big deals but for me it would be a long term niggle. On the plus side a very well respected unit, good interface and sound. It will be easier to improve speakers and amps etc.
The Kenwood's of the past seem to get little love both here and with the installers I talked to. One installer said they installed 10 Pioneers to every 1 Kenwood unit.
However another installer said that the 516 unit was very different from the previous units and he is recommending them over Alpine, his previous 'go to'.
I have to say though I decided to remove this from my order as I was not prepared to take the risk and can't say I like the user interface.
Summary - For me a well integrated system was the priority and so the VW option won with the Pioneer being a very close second.
4Motion - Have decide to add this, I live in Scotland and often drive home 2-3 hours late at night / early morning and during the winter the 4x4 will make me feel safer.
My current vehicle is 4x4 so kind of want to keep the status quo. BTW I had to move from the T30 to the T32, VW don't allow the combo to have 6 seats & 4 motion on the T30. Something to do with vehicle wait vs load capacity.
Last decisions to be made is 30mm Eibach vs H&R 40mm and wheel size and type.
I will borrow a friends T5 Sportline for a drive tomorrow and see what I think of the Eibach's.