Some of the snacks are Nakd bars and Nairns oat biscuits (ginger, fruit & spice and a berry I think). The porridge would be the same as any, as long as it was low/zero sugar.
Having said that, I would think that buying it all separately would probably not save much, if any (in fact could be dearer buying individual meals).
One problem I would have is with the preparing my own healthy meal... then the onus would be on me to make the right choices about content and size of the meal. DC proper does this all for you. You know that as long as you stick to their food, you HAVE to lose weight, because it's below even a sedentary lifestyle maintenance calorie level.
DC seems to me to be the most reasonably priced of any diet... and certainly better than my Mum's outlay of around £5 per day for 2 meal replacement products