Two things that occur to me:
1. The price is right, put it up at £6150 as everyone knows they will offer or do a deal around £6000 as that's what this price is enticing, we all know it - everyone wants a deal as it makes them feel better about their purchase. If I see a car for £5999, I think I'll buy it for £5500 and so on.
2. The pictures I feel need to be somewhere better, a good quality photo is key as that's the first thing people see and as the old saying goes, "a picture tells a 1000 words". First impressions count. It's like selling a house, getting people in to see it is the hardest bit.
Also, rather controversially, people who complain about the hard economic times shouldn't be buying a Mercedes, they are not cheap to run, they are not cheap to buy and they are not cheap to maintain - everyone knows this, it's always been the way so don't get pressured into a sale. People who are serious, do their homework, know how much they should be paying and hence, are the people you are targeting.