biglips - doesn't your sister have the internet? If so she can pay the money into your bank account online - no excuse.
my biggest money saving tips are:
look on uswitch to check you are with the cheapest energy providers
keep all leftovers for lunch next day/to give dc for their dinner/freeze.
each week look at what you have left before you go shopping again and meal plan. try to make the most of what you have and only buy the extra things you need to make the meals on the plan for the next week.
if you are inclined to buy takeaways when you can't be arsed to cook then cook things in bulk and then put into portions and freeze so you can reheat those instead of buying a takeaway or ready meal.
Eat more meat free meals. We do this to save money and what meat we do buy comes from the market.
Use Lidl/Aldi/Netto for for half price fruit and veg, tinned beans, chickpeas etc, frozen peas, olive oil (we decant it into a spray bottle so you use less), fresh herbs, tuna, tinned tomatoes, noodles, eggs, cheese, milk, plain yogurt, butter, frozen fish, free range chicken, dishwasher powder, washing up liquid, washing powder. Then we go to Asda for unrefined sugar, wholemeal flour, wholemeal pasta, brown rice, salt free pasatta, porridge, shredded wheat, salt and sugar free muesli, bread (you could make your own if you wanted to be really good), spices, bouillon powder and other stuff you can't get in Lidl.