I would always go the newspaper/magazine route for the simple reason that Renault won't care about individual complainants turning up at dealerships but they will care about a PR
trainwreck in the national press.
Give Renault a chance to respond but then take your story and backstory to someone like Haymarket (What Car? et al).
Having said that I would be inclined to wonder if GC might have put his finger on the problem here, in that a total lack of regen when lifting your foot from the throttle and gently applying the foot brake - my car's done it on numerous occasions, leading me to start a thread here wondering if the regen levels were dynamic - can feel
like the car is getting faster, whereas it is in fact merely not slowing as quickly as your brain is expecting.
You can see how your senses might get confused, particularly in an instance when you've had the same sort of vehicle misbehave previously. And I can totally see how you no longer trust it.