Engine Cutting out

Hi

I've recently purchased a second hand 307. I've only had it a couple of weeks and on 3 occassions the engine has cut out when I've slowed down to approach a junction or roundabout. The first time it happened (day 5) I put it down to the fact that it was me! but as it's happened another 2 times I know it's not me! I don't recall seeing any warning lights on the dash but everything stops, including the stereo which is how I first come to notice that the engine has stopped due (due to engine beng so quite! It does start again straight away.

I've taken it back to the Peugeot dealer who I bought it from (3 months warranty!) who have said that they can't find anything wrong with it, no fault codes etc and as it is an intermittent problem, sods law it wasn't happened when they've tested it.
Any suggestions?? obviously want to get it sorted before the warranty runs out.

Cheers