I'm using Tresemme naturals as a diluted scalp wash before washing with conditioner. The benefits of no SLS are less irritation, less stripping of the hair's natural oils and less over-production of oils, so you shouldn't need to wash quite so much.
It can take a bit of adjustment to get used to it as it's less foamy and it takes more work to make it work, as SLS is a harsh detergent that foams readily. IME diluting non-SLS shampoo really improves how it works.
I get FiH in the health food shop, it is widely available, I live in rural Scotland and never have a problem getting it, for me the benefits are my hair feels better using it compared to normal high street brands, I prefer using it on my dc, it feels luxurious without being expensive. It is an ethical company afaik, and if my hair needs a change I know I can get a different one easily because they have a good variety.
I like the chocolate one, and so does my ds! The hemp & meadowfoam and the seaweed ones smell really lovely too. It generally lasts for ages, if I use high street stuff my hair always feels pretty horrible, so I always go back to FiH.