After a good few years of my very fine hair looking more and more thin, flat and visible scalp on top and trying all sorts, I have come to a working solution.
Its helping me , so might help others.
Got this by chance in TK Max - they had big bottles in one day : www.amazon.co.uk/Fitzrovia-Centre-Thickening-Paraben-Free-Salon-tested/dp/B073CZ6PYS/ref=sr_1_1_a_it?keywords=fitzrovia&tag=mumsnetforum-21&ie=UTF8&qid=1534148864&sr=8-1
and following a mumsnet recommendation I ditched the john freida serum and am now using Elnett Crème de Mousse volume for curly hair.
I wouldn't say my hair is massively thicker but the overall appearance is much thicker and much less visible scalp.