Recommendations needed for face serum

[bgottalent]

I'vebeen using Obagi professional c serum 15% for the last 6 months and it's about to run out. I'm happy with it but as it's expensive (as are all serums) I wonder if I should try something else.
Do any mumsnetters have a favourite serum that they would recommend?

I've tried all sorts of serums but my favourites are
Alpha H intensive night repair serum £45
Superdrug simply pure hydrating serum £3
Aldi Q10 £3.49
Bravura Hylauronic £25