I would say if you want to pour the cream then I would use single. I have this argument everytime with my mum, when she gets double cream, but then doesn't whip it - to me it defeats the point of having double cream. I personally think that double and whipping cream should always be whipped.
Thanks all
When I used to work in a restaurant they always used to buy whipping cream for the desserts to pour over, without whipping, always confused me!