I just tried the TetenalUK site and if this is an example of Tetenal in general then I agree it is far from user friendly. The webmaster has done a poor job under fixers as I could only get to a hardener product!!. However if you do a search on the site supplying the name such as Superfix then it will show you the product and give dilution and capacity.
An Ilford website it is not. There is the bare minimum there but you have to do the work. There might be full specs somewhere but user friendly like the Ilford site with full instructions it is not