i just sold my E55 estate last week.
only place i advertised was on pistonheads, and the first person that called bought it.:bannana:
i only had 3 callers about the car, all were 100% genuine, and all 3 were happy enough to travel from London to me in the east coast of Scotland.
do the premium ad ( £15 i think ) gets you 1 month and 9 pics or so; take time with the pics ie take a bit of time and take them somewhere nice rather than a driveway or a street, do not waste duplicating similar images, get front, rear, sides, sides looking down lenth of car, alloy close-up and interior shots with no crap in door trays etc, it's your ad so do a bullet point list of every feature and extra the car has; you will be amazed how many features you soon rack up with the E55.
if your pics are good, your description clear, it can help weed out the timewasters, whom usually start the coversation with offering you 20% less than the asking price
Hope some of this helps, and all the best with the sale.