Don't know if anybody has the same however here goes.

My 120i parking sensors gave up 3weeks ago, it upset all the dashboard lights too! This car was new in March 2010 it has now only 18250 miles on the clock looks like new (thank my wife for that!)
Anyway we sent it back to BMW where they found a water in the boot got into control unit.

Now this car had a SMALL repair where a young lad run into the back of us (Sept 2012) (new bumper and a little dent in boot lid) this work was all done at BMW (ever got a certificate of repair, 3years) It never been to any other garage apart from BMW!

Bmw say nothing to do with them, Have been chatting to them for aweek (waste of time!!). In the end I got it back (after aweek!)when I paid £96.00 (Investigate parking sensors)

I know this car is over 3 years old but a water leak on a car of this age? they said they can fix it at first for around £600 now got it down to £380 (they will pay for parts! how kind!!)

Whats best way forward? And please don't say phone BMW customer help line because they are useless! :-(