Id say at least £300 for a proper going over by a pro detailer. You'd be suprised at renault tbh mate, find the number for renault uk and explain the situation to them.
I had the engine wiring loom snap in my 57 plate r26, meaning i couldnt start the engine or nothing. Told it was £650 to fix, i phoned renault and a nice chap called harvinder or something, one of their managers, sorted it so they paid £500 of the £650 which i was chuffed with as it was way outta warranty!