Yes, I sometime have to struggle along with such a small amount of chocolate, as well.
Try to ignore the financial aspects of your problem and start your day with a decent breakfast of at least 6 Mars bars. Then you can get back into the swing of things, with a Topic, Boost or whatever every half hour.
Remember that the major supermarkets are now selling quite big Easter eggs for just a quid each, so you should be able to afford a few of those each day.
I hope that you can soon get back to sensible levels of chocolate consumption (equivalent, for example, to half a Thornton's shop every day).