I've haven't used a lot of intensive care treatments apart from vo5 hot oil a long time ago. However I've tried many conditioners & the best by far for me (Hi-lights, blow dried, heated curlers etc!) is Garnier Nutralia moisturising cream conditioner. Oddly enough it's one of the cheapest & the only place I can find it is in Savers but I love it!
henna conditioning treatment is very good. Generally you can only get good ones from salons or hairdressing suppliers and you do have to use it quite frequently but it does make a difference. You can also buy a spray that you put on your dry hair before you straighten it which acts as a kind of barrier.
I blowdry and straighten my hair every other day and I use the Linco Beer Company treatment (I think that's what it's called). It comes in a little yellow sachet and Superdrug do it for 99p. It smells fab and leaves your hair thick and smooth and gorgeous. No I don'twork for them
Beware of henna treatments if you have coloured hair, they can change or lift the colour. My hair is dry, thick, wavy and colour treated so I've tried hundreds. For serious conditioning I recommend Redken All Soft Heavy Cream, which is expensive but fab. A more affordable one is John Frieda Beach Blonde Kelp Help.