In my opinion it's not worth it, StudyClix has far more resources than any of those books. Between exam papers, mock papers & your textbook, there is more than enough content freely available.
So no, it's not worth it, not even by a longshot.
Useful advice :Absolutely worth it. Less Stress, More Success would be the best one to use depending on what subjects, or any ReviseWise text books whatsoever. They have great revision tips and guidelines. I use them and they work really well for me.