Engine cutting

[Wilsomb83]

Hi,

I’m here in the hope someone on the forum might be able to help me. Firstly, I just want to explain I know naff all about cars so if I don’t call something the correct name or explain in great details I’m sorry and please don’t take the mick. 
Vauxhall Astra 09 plate, regularly serviced and MOT’d has recently starting cutting on me. It done it mainly when I need to slow to turn a corner or at a roundabout etc but also I left the engine to run and it sounds quite normal for a second and then it dips and then normal and will then cut out. There are no warning lights and husband ran a basic diagnostic check with no issue returned. He has replaced some type of filters, checked the oil and also put some stuff in to clean the diesel (I think) as the car is a second car it’s only used locally for tipping about in so it’s not high on mileage but does get used at least every second day. He also bought a replacement suction control valve as when he has looked online it points him to this but we think he ordered the wrong part so we have another (hopefully correct) one on the way. Has anyone on here experienced this issue? If so did you manage to resolve without needing it to go to the garage or spending a small fortune? 
thanks in advance