When I contacted the guys over at Blitz Publications, they advised me that a very small percentage actually COMPLETE the challenge. You didn't fail at all and deserve a big congratulations for making significant changes in your lifestyle over the 12 week period. With the lack of support you received and the emotional struggle you endured, this is an achievement in itself - not many people would be able to do what you have done.
In addition to this, if you have been eating well and exercising, there is no doubt that your health has improved. Do you not feel any better within yourself?
Now if you're considering entering into another 12 week challenge, consider the previous challenge as a trial run. You now have some experience under your belt from which you can build upon. It is very important that educate yourself and learn how to achieve your desired goals. An excellent resource to learn about health and fitness is this website.
I would also highly recommend a personal trainer to provide knowledge, inspiration and motivation for you throughout your 12 week challenge. A relatively small financial investment goes a LONG way when it comes to your health and wellbeing.