Depends how desperate you are for a Driving job, it will definetely help, but nothing will 100% guarantee a job in the end, and a lot of it is luck! Especially the app forms and final line manager interview. This not only goes for Driving but getting any job on the railway.
I bought the cheap original How2Become DVD for £14, it helps get through some of the stages, but its not enough to guarantee anything, the platinum package looks a lot more in depth and probably helps a lot more. I wish I had this package available from the start as I've failed so many Interviews its unbelievable, but its not much use to me now, as I've already passed the tests a couple of times, and done so many Interviews, theres probably not a lot more I could learn about the process, and I'm in no rush to make the move.