Hey Hey!! Don't be negative over this... it truelly won't help.
In terms of doing Cambridge then how much do you normally spend on food a week for yourself? Including snacks, drinks, treats, meals out and normal supermarket shopping? Make sure you are sure that it is due to money and nothing else.
And if you really can't afford it then why not do the Cambridge 1500 programme, this is only around £10 a week and means you will still lose weight (albeit slower) and also have the meet with your counsellor to make sure you are losing weight and also have that motivation.
If you decide then you simply can't do Cambridge anymore for any reason (including money) then that doesn't mean you must put weight on, if you want to maintain long term then you need to be able to find moderation in terms of what you eat, there are many tools for doing this in terms of calorie counting websites etc, why not do a free trial at
Weight Loss Resources and see how you get on.
But admitting defeat won't help, it will mean you do go back to the dark side so remaining positive about this is key, you haven't put all the weight back on and if you can relax and take control of yourself and your weight then whatever method you use then within a few weeks you will be back on track and trimming off the pounds.
Mike