Grand Scenic 54 1.9 dci?

Quick background!!! Bought Grand Scenic DCI1.9 120 Priv in May 2007, Renault warranty till October the extended till Oct 2009. First 7 months from 37 000 to 44 000 miles lovely drive! New Year 07/08 dashboard blew up and heater resistor pack failed!!! Warranty paid and repaired. Jan 08 all proximity door locks failed, again warranty honoured and repaird. Feb 08 oil very sludgy and low, booked in for service 6 000 short of recommended, and since service the following. 1 week after back in due to low oil, after a few weeks Turbo replaced with intercooloer and inlet pipes. 2 weeks later back in low oil, Renault advise NFF. back in again after top up 1 week later, after a few weeks accelerator housing replaced due to leak. Car has been in and out nearly every second week till November. Renault say Turbo faulty again. Sent away, turbo fine but damage to several fins. Again repaired and extended covered cost. Back in again december mid month and still there, renault advise new engine, but extended not buying, as report say fair wear and tear!!!!! Car has done 55 000 and this has been an issue since Jan/Feb 08. Engine has also had 2 engine flushes and 8 heater plugs, but bores well worn, big end shells are picking up. Renault feel excesive for milage, extended say normal, but still no confirmation on why I use 1 litre of oil for every 500 miles. Any advice on possible problems and what would be deemed fair wear and tear? ps Extended warranty with Peugeot (french!!!)