Hi, what an awful experience, you have my sympathy!
Turbo failure is indeed a common problem with the dci engine (I've had it happen twice)and in fact many other
turbo diesels, but it would seem that when the Renault one fails it does so in a very dramatic fashion, often ruining the engine. I've personally never heard of it resulting in a fire but I guess it can happen.
If I read your post correctly it seems you managed to get the engine stalled and the garage isn't talking about engine damage so it should be ok.
However £3000 sounds way too much for what they're talking about replacing-I presume this is a Renault main dealer? If so I'd suggest you go to a good local independent garage. Ask them to source a good reconditioned
turbo (or do so yourself -expect to pay around £350 for one on
Ebay for example or googling dci
turbo will bring up plenty of recon companies), an aftermarket cat if they reckon it's needed and possibly an intercooler. A good garage will know what they're doing but it's vital that as well as cleaning/replacing the intercooler all the
turbo pipework is thoroughly cleaned to remove all traces of the shattered vanes from the old
turbo. Going this way, you should be able to get back on the road for about £1000-still a lot of money but much less than £3000!
As to who you could complain to,
Renault Customer Services would be your main option. Personally though I don't think you'll get much satisfaction from them. It would be worth checking the cars' service history to see if it's had a
turbo replaced before. At 160k I'd be amazed if it hadn't as 90k seems to be the average lifespan for a dci turbocharger, and if it has and it was fitted and regularly serviced since by the main dealer, you might squeeze a goodwill contribution out of
RCS. But they'll only do this if the work is done by their dealer which means you'll pay more even with their contribution than you would at an indie.
As to whether you fix or scrap, personally at £1k I'd fix it. The dci engine is basically pretty robust, many see service in taxis and vans and go on to mileages well over 250k. Regular servicing and in particular
oil changes with fully synthetic
oil are the key here. The fact yours has a full service history is reassuring. In most other respects the Scenic should be as reliable as the majority of its' peers.
Good luck and I hope you get it sorted!