I have a Peugeot 108 with the 1.2 puretec engine. When it is cold it does something a bit odd. in 2nd, if you put your foot down, it is a bit sluggish for a second or two then comes to life. It feels a bit like turbo lag, but it isn't a turbo. When it warms up, it doesn't do it. What's going on?

I don't know about the engine itself, but that suggests a temperature sensor issue messing up the cold fueling.

Second that poss temp sensor problem , surely it's under warranty ?

Interesting idea. I'd wondered if it was an emissions thing, with the throttle opening limited for a few seconds. it runs smoothly and then you get an extra 10 or 20%.

My experience with throttle by wire cars is exactly that, depending on warmup status etc they will just infuriatingly limit throttle transients.