Has anyone used either of these? I feel my skin could do with a bit of extra help at bedtime now. I never usually bother using moisturiser at night (rightly or wrongly) but as the weather's now got a bit colder maybe it would be a good idea. As I know virtually nothing about serums, could I use this by itself or would it also need a moisturiser putting on top? Or would I do just as well just to use the night cream? Thanks!