I have been told delievery is FROM September 07. The official launch in UK is Sept 8th. Rumours are around that some deliveries will take place before this.
There is no information on the BMW build system the dealers have to date. First cars for UK to be built will be demos for press, then it will be down to where your dealer lies in the pecking order, how many they will be allocated and then when your car falls in the order system.
If you have ordered your car, you should have an order nr. This will be how you can track it's progress. I have found BMW UK customer services very helpful, so you could ask them, but there won't be any info on dates until late June/July.
Like you, I just want to know the date. Be like me and keep badgering them every week