Did WW several years back, lost 2 stone. Gradually put it back plus a little more. Joined again, only went to 1 meeting before I realised that the same would happen again, and cost me! Been doing the 5:2 for 11 months, lost 3st and reached first goal. It has become an eating way of life. Can be tricky at first, but when you see the weight go, it's the best motivator. Also you can eat anything you want, even on fast days, as long as only 500cals. Try to plan a 500 cal menu in advance for fast days, it helps.
BBC did a diet comparison programme, based on cost, the cost per pound lost was huge.( can't remember exactly, but 10s of £s)
Lots of support from gransnetters who are making the same journey. Good luck. XX