I concure, you have a contract that states it has sat nav, they can't just say "sorry we didn't know what we were looking at"

You're looking at the thick end of £600-£800.

Do you have the original advert as proof.

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Sept 03, M3, Silver Grey. Retro-fits: Modded Mk4 DVD Drive, OEM Bluetooth, VR Control, Rainbow Speaker Upgrade, Sony SOT Amp, HK Sub, CCFL, Intravee II, NightMode.