Success rates or reviews of Brain Working Recursive Therapy (BWRT), and number of sessions needed on average Brain Working Recursive Therapy (BWRT), introduced by hypnotherapist Terrence Watts in 2011, is a brand new form of therapy. Hence, my internet search doesn't seem to give me any idea of how successful it really is. Here's a link to the official page of BWRT: https://www.bwrt.org/. It hasn't got a wikipidea page yet.

How many sessions of BWRT does one need in general to cure one specific problem? 

If you could cite any links or even your personal experience, I'd greatly appreciate it!
Looking at the client testimonials on the website you provided it looks like it varies from 1 session to a few more.  Like any other therapy it seems to depend on the client and problem being dealt with.

You could ask the therapist how many sessions you are likely to need for your problem in order to find out whether you would like to go ahead or not.

I am really interested in this and I am going to look at this therapy in some detail as it is interesting to me considering it is supposedly not a remodel of NLP, EFT, TFT, WSN, SD, EMDR, Hypnosis, Reiki, Meridian/Energy therapies, Noesiology, Chinosis or any other style of therapy according to the home page.