A couple of the ladies in my group are having a similar problem in that they seem to have plateaued for a few weeks. My consultant suggested that for one week they consider following one of the sample 7 day menus on the Slimming World website. There's an Extra Easy SP menu on there, which might help boost you in the right direction if you've been stuck for a while. Last weigh-in one of them did follow a menu for the week and managed a 2lb loss so it may be that you just need to mix things up a bit.
Do you find that you eat similar things each day for your syns and healthy extras? If so, could you have a bit more variety? I try to use at least 3 different things for my HEBs each week (for me, usually bread one day, oats 2-3 days and nuts for the rest of the days) and try to maintain a balance of milk and cheese for the HEAs (though cheese often wins...).
I also find that the weeks I don't drink much water are the weeks where my losses are smaller. When I up my water intake my losses seem to show more (I basically live on coffee during the day so I have to make a conscious effort to drink more water). Is this something that you think might help?
Also, huge well done for not caving with the cakes! That's some serious willpower!