I would say that swapping to WW would definitely end up being more expensive than swapping to CD. Even though it's free to register at the moment, the meetings are £4.95 each. If CD is £32.50, you'd have to spend less than £27.45 a week on food to spend less. You will definitely be doing it for much longer than if you just lose the weight on CD thereby making it even more expensive.
For example... say you want to lose 15lb.
CD
If CD averages out at 3lbs a week that's 5 weeks @ £32.50 a week.
Total = £162.50
WW
Personally I would be very lucky to average 1.5lbs a week on WWs (but of course I don't know your personal circumstances how much will power you have/how much you want to lose etc) -
so that's 10 weeks of meetings at £5 per meeting - £50
Say you spend £20 a week on your food bill - £200
Total = £250
Basically in this scenario your weekly food bill would have to come to no more than £11.25 a week to make WW even
as cheap - let alone cheaper than CD.
Anyway, obviously I have no idea how much you want to lose - how much you would spend on food etc etc... I just think it would be very unlikely to be cheaper and it would certainly take longer and if you're anything like me at all, you will put weight on!
That being said, others fare very well with WWers.

You could also just not go to meetings which will save you
some money
. I have always got my support through the WWers forums where there are many people like me who have done WWers for years and years and know the whole points/no count thing inside out.
Whatever you decide, I'm so sorry to hear about your relationship and I hope that things get a bit easier for you. If it were me I'd be tempted to eat for Britain even though what I would
really want to do is make a brand, shiny new me, full of confidence and able to go out there and knock 'em all dead!!
Good luck!
