My suggestion is to do one thing at a time. Introduce a new step every three weeks (apparently it takes that long to become habit). I woudl start with introducing H2O into your daily diet (even if it's only a glass a day) and have a healthy breakfast (yoghurt is a good breakfast too - not yogo :P but proper full-fat yoghurt), then introduce the apple snack, then incoporate a better lunch, etc.

But I would aim to have the plan you've put together happening by October/November. Otherwise it will all seem a bit hard and when you DO have that packet of Tim Tams, don't think 'Oh - I've done it now, I've failed' - instead 'whoops! Get back on it tomorrow!'.

Good luck! xxx