I recommend http://www.auctioncarbuyer.co.uk/About-AuctionCarBuyer.htm We bought a car from an auction via him. Only costs about £100-£200 more than going yourself. He has contacts and buyers at nearly all the auction sites. Our car came from Preston. Saved between £1-2.5K. But the car has full history. No high miles or long time since the last service. Dealers are notorious at buying company cars with 120k+ knocking 50k off and throwing away a few service chitties so you end up with a 70k car that was serviced in jan last year.
RE: Diesel cars... I've got an 04 Seat Ibiza 1.9 TDI goes like **** of a shovel and noise isn't a problem. I normally get about 450 miles out of a tank of diesel as well... not bad going.
only 450 miles a tank I get that out of my 3 litre V6 petrol Which really is rapid. Mind you its a 60 litre tank ff