Faith In Nature Organic Rosemary Conditioner 5L (£37.90 / £33.91 max S&S)

A 5 litre bottle of Faith In Nature organic rosemary conditioner for normal hair and scalp is £39.89 at Amazon, which works out at about 80p per 100ml.
It is made with organic rosemary oil, and Faith In Nature says it helps leave hair fuller, softer and healthier. It is suitable for normal hair and scalp, and is paraben free.
The huge 5 litre size is designed for refilling smaller bottles, so it is great for a big household, a salon, or anyone who wants to cut down on plastic bottles and stock up for months. It pairs well with the matching Faith In Nature rosemary shampoo.
It is rated 4.4 out of 5 from over 13,000 ratings on Amazon. It was in stock at the time of posting. Sold by Amazon. Free delivery for Prime members or on qualifying orders.