Thanks for all the replies, im beginning to agree with the theories that they got the initial diagnosis wrong.

Problem was that I got the car diagnosed 1 day before warranty ran out! As it stands the car is now out of warranty by 1 month. Hopefully there is no issue with warranty as I did alert them of the fault prior to warranty running out.

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2009 135i M Sport Convertible
2008 X5 3.0si
2003 E46 318Ti M Sport Compact - donated to parents
2003 116i Hatchback - donated to brother
2002 316Ti - Sold
2000 318ci M Sport - Sold
1998 318i Sedan - Sold