You say you're a yoyo dieter so I presume by that you've tried every diet going so you've probably been to Weight Watchers at some point?
Why do you feel the Cambridge Diet will be the one that works? Do you really think the Cambridge Diet is the best one around or could it be that you've finally decided that this time is the right time for you to lose the weight?
I lost five and half stone in 2002 (Like you I was approaching 30 and felt if I didn't do it then I never would!) by eating one meal a day and exercising like a Trojan. I lost the weight too quickly and was left with loose skin and thinning hair. Not healthy. No quick weight loss plan is when there's more than a few lbs to lose.
I had another baby in 2006 and joined Weight Watchers to help me lose a stone as I just couldn't face the one meal a day plan again. I wish I'd joined in 2002! I was never hungry, had lots of support and the weekly weigh in was a good incentive to stick to my points allowance.
I don't know much about the Cambridge Diet other than it's a meal replacement plan and that a lot of followers complain of constant hunger. But the weight loss is quick so that keeps them going.
You can't eat liquids forever though so what's to stop you overeating when you start to re-introduce solid foods?
Having lost a lot of weight myself I really believe you have to find a weight loss plan that you can stick to fovever! I couldn't eat one meal a day forever because I was hungry and the hair loss proved it was making me ill. The human body needs more than one meal a day and it needs more than liquid.
You sound determined this time so why not choose an eating plan where you can eat real food in the right amounts for your weight to allow your body to stay healthy but to also lose the excess weight. Weight Watchers will help you with this.
Also, think about other changes you could make. I know it's hard on these wet cold days to get up the energy to go outside but when you feel a snack attack coming on pull on your shoes and take a 20 minute walk. You'll feel so much better for it and when you get back you won't want the biscuits/crisps because you won't want to undo the good that walk just did you.
I know I've gone on a bit but I feel so passionately that you don't need a faddy diet to shift a large amount of weight. I wish you the best of luck with this diet and am very interested in how much lose but please think about Weight Watchers.