Renault did extend the warranty - well pointed out Kingboy.
There is a ton of information about this on
www.renaultforums.com
My car has still only done 63K but because it did not have a fully stamped service book they dismissed it out of hand, even though the car had been serviced by competent mechanics (it was a company car owned by my friend so I know it was well looked after and serviced on the dot each and every time!)
As Kingboy pointed out,the engine has been drawing the oil from the turbo and thd feeding itself on that, hence why it didn't respond to the stop button. This is due to the oil burning in the engine and the exhaust gases are recycled through the EGR valve. If this gets sooted up (and it does too 4king easily) the valve sticks open and the revs go higher, drawing more oil into the engine, causing more soot, causing more revs, drawing more oil............until the oil runs out.
The EGR valve can be cleaned easily (renaultforums have lots of detail so I won't reinvent the wheel)
When my turbo went the shaft did snap as Kingboy said, and it is 99.99% certain your's will have too. When you take the old turbo off you will see the vanes on the turbo spline will have broken off and been sucked into the engine. Sounds bad but don't worry too much. If the engine is still turning over with no problem (apart form the obvious lack of power) then you can be pretty confident that the small bits of vane have been either crushed into the piston head or blown right through.
Garretts and Renaults - bit like women with driving licenses - bad idea!!
Renault did shorten the service interval for oil for these but never did much of a publicity campaign - what a surprise!
I'll try and put some guidance notes together for you mate. If you were a bit nearer I'd come and give you a hand, but I'm stuck in Warrington I'm afraid.
I'll post something on Thursday afternoon hopefully!