Well, it turns out the low calorie days did the trick as I managed to lose a pound after all. That makes 11lbs in six weeks, which is not bad, but... six of those went in the first week so it's not exactly brilliant, and more importantly it's not going to be sufficient to jit my March target.
So... I am intending to go back on the Slimming World plan for two or three weeks, hopefully this will give me a boost and knock a good few pounds off and build me a buffer again. I can't really face the SW diet indefinitely, because you aren't allowed granary bread . Which sucks.. and I'm not using my 'syns' on bread. Or anything except chocolate, except possibly crisps and dip.
When I used to go to Slimming World they did say you don't have to have your fifteen syns (like points, basically 20c = 1 syn, for food that isn't 'free', which is meat, fruit, veg) each day, you can have them all at once if you like, as long as you can manage the rest of the week without. I think it would be better to start on a Monday, as I'd rather save Syns for the weekend, rather than use them in advance.
So that's why this week my days are running Saturday- Sunday, so I can start SW on Monday.