Hi readyfor, sounds like a good plan to try and aim for a more long term weight loss now, especially as you have managed to lose a large proportion on the cambridge diet and only have 2.5 stones to lose.
It is worth registering on the SW online 'lifeline' as you can put your target in and it shows each week as you moe towards it and gives a timeline of when you would hit your target.
I find it useful as I can think, oh by March I will be...
Porky, I can imagine you are disappointed, but at my group, some people seem to not lose for a week or two and then lose a big chunk, almost as if their body takes a while to catch up with the diet iyswim. don't give up! Maybe you could ask your group leader to look over your diet plan, just to make you feel more confident about what you are eating. I do think though, you will probably just see the benefit next week.