I have looked at these people and thought it was intensive and expensive ( maybe you get what you pay for ! ). One hour a night is a lot, probably to much, leading to a lack of motivation. They seem to do a lot of time consuming vocab. work.
What are you trying to achieve? I presume a place at a Slough grammar, why not work towards that goal on a DIY basis over the summer, I found thirty minutes four times a week was the most we could do in the run up to Reading School exam last year.
They do claim good results, maybe only the strong survive.
I have not answered your question because I think encouraging a child to do one hour a day every day is counter productive.