How shopping and eating on a budget really works at the moment. When you are on a tight budget you figure out what you have to spend on essentials each week. You basically allocate set amounts for rent/mortgage, energy, household bills, and then food. These are fixed amounts and rarely deviate from week to week. Let’s say a large energy bill arrives (as has happened for almost everyone in the past 3 weeks) and it puts your entire budget into chaos. The trouble is that you still have the same budget and income. You can’t reduce your housing bill; that’s not how renting or having a mortgage works. You’ve also…