new car

hi all , i am looking to buy a new car. this will be my 2nd car having had a 03 vw golf which has served me well. My budget now is 9000 but i would be willing to hold out for a couple of more weeks to get it to 12000 if needed. I dont know a whole pile about cars so am looking for some help. so far the conclusions i have come to are a bmw 5 series or an audi a4. It would have to be diesel. right now i am looking at bmw along the lines of the one in the first link below but am worried of the timing chain issues which is putting me off buying a bmw is there any bmw between 05 and 09 that dont have this issue, my second option would be to hold out a few more weeks for an audi such as the 2nd link but they tend to have high mileage if i spend 12000 on a car surely is should expect less mileage than 120000 miles or is that ok? i have my heart set on a bmw or audi but would listen to other recomendations also should i buy from a dealer or privately and how much should i expect to haggle a dealer down to ? any help would be appreciated