I have used Confused to compare prices....
In terms of declaring factory options, my understanding has always been that if they are fitted at the factory then you don't have to declare them however if you or the dealer added them then you do. Consequently with over £4k of a.c.shnitzer bits on my current car my premium was about 1200k, with about 2-300 quid added just for the extras!
Current: E90 335d (May 2007) | Black/Black | Prof Hifi | Prof Nav | 6FL | Fully Electric Seats | Xenons | Folding Mirrors | PDC
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