Update from previous message !!
From the previous post you will recall that the Bass and Treble were far too high and almost zero mid range.
On reading several posts it was becoming clear that I might well have connected the Diplexor incorrectly due to the rather strange marking on each of the wires. Took the door panels off again !!
Sure enough the wires were connected to the wrong way round !! Thanks BMW/Alpine for such confusing labels on the cables !!!
Once it was all back together again it now works fine and I am really impressed with the final result. You need to accept that you still have the crap speakers in the back but they only really fill in a bit of mid range.
So I can confirm that for the late 2011 BMW X1 with the Professional Head Unit that it does not appear to need re-coding and the balance between the Subs, Mid range and Tweeter seem to be OK. The switch on the Alpine Amp was set to "1".
Just make sure when you are fitting this Upgrade you have the latest fitting instructions dated 07/2011 as these appear to be the most accurate.
Anyone needing help with trim removal I am now an expert !!
It might take an experienced dealer technician 2 hours but for your average DIYer I think you need to give yourself 4 or 5 hours to work it all out !!
I would certainly recommend this upgrade for anyone with the basic speaker set up and it is not so difficult to install for a competent DIY enthusiast - Any one else should get BMW to do the upgrade.