Had an interesting response from BMW UK today. After receiving a cheque from the local dealer for £108 , I complained to BMW UK, they have said that the offer represented 80% of the cost of the part excluding VAT. My problem is the part cost £212.13 excluding VAT so someone at the dealer I suspect is not very good at maths or !!!!
In addition and if it helps anyone else I phonedanother local BMW dealer and found that they had supplied 6 rear offside lights to 2009 reg Z4 owners in the last 12 months. Even they admitted it was ahigh proportion considering how many they sold.