It is worth saying that groceries can be cheaper at other supermarkets like Aldi, Tesco or Asda. Waitrose is often more expensive. Waitrose is like Tokyu, Aldi is like Seiyu. If that helps. Also, if you're going to be in the UK for a while, you can look into the rewards clubs at the supermarkets. E.g., Tesco Clubcard could save you 20-30% on many items and you'll earn points for discounts or vouchers at restaurants or other activities. I feel like a salesman now.