Fumes from the back?
hmmmm, suggests a problem with the filler neck where it joins to the tank or a leaky/damaged fuel filter (usually a red bull can sized thing, normally to be found underneath the car beside the fuel tank on most cars)
A blocked vent on the filler pipe could certainly cause bother also.
At the end of the day, any kind of fuel leak could cause all these problems as the pressure in the system doesn't remain constant, allowing the engine to wander a bit due to air in the system and lack of constant pressure.
Has to be said that the engine usually tries to stall when you start it the first couple of times when you have a fuel leak, so really got a few ideas but stumped at the same time LOL.
so many things can cause bother - even a clogged air filter/dodgy spark plugs can cause these kind of running issues.
Try an independant
renault garage, a diagnostic at my local indie renault place is £70.
Other garages will also be able to investigate and are likely to charge a little bit less, just make sure and get a quote for the initial work first. Most garages have good enough equipment to read fault codes and fault find running problems.
Just make sure it's a reputable garage. ( I'd say Renault would be best if I had any faith in them at all.) At least they can be held accountable to a degree as they represent a brand.
This is the problem with cars, far too much to go wrong these days, ahhhhh how I miss my VW Baja bug..my old mini, my Lancia Delta.........
(zzzzzt - record scratches - did I say the Lancia Delta....scrub that, what a painful car LOL)
If you happen to live in central Scotland I'd be more than happy to come and have a crawl about under the car, it's not something I normally do - meeting with folk off the internet - but seeing as how you're a damsel in distress... LOL I wouldn't charge anything either, I'll just settle for a cup of tea.
If not then the best bet is to take the hit and go to the garage with it, at least then you will be able to tell us what on earth was causing it and you'll know it's sorted.
At least for another couple of weeks anyway, given that it's a Renault.