Bumble & Bumble Hairdresser's Invisible Oil Primer is AMAZING - not cheap but the best thing I have ever used on my long, thick, wavy hair that needs a lot of heat styling to look decent!
It's got heat and UV protection, but also has lightweight oils to help moisturise, plus it actually (weirdly) helps my blow dry last a day longer! So less washing. It's incredible and I've stockpiled it! The hair oil from the same range is also v good.