It's common knowledge that the UK is not particularly known for its culinary delights. While there are excellent restaurants in London, you can expect to pay through your nose for them. So what does a tourist with a limited budget and time do?
This is where M&S (Marks & Spencers) Food, Tesco Express, and Sainsbury Local can save your wallet.
As urban, convenience-store branches of their supermarket parents, you can pick up anything from a light snack to a full microwaveable meal. For those who think this means it'll be high in fat and innutritious, you'll be glad to know that the majority of options are low-fat, with no preservatives with even some organic choices.
For lunch on the go, I recommend picking up a sandwich or a wrap, a juice/smoothie, and a piece of fruit in the morning. It'll run about £5 and be much tastier and healthier than anything you can get in tourist areas. If you're travelling with a friend, there are usually discounts for buying 2 of the same smoothie, further saving you money!
If you have access to a microwave (such as hostel dwellers), you'll have a lot of healthy and tasty options, ranging from chicken tikka masala (supposedly the most popular dish in the UK) to lasagna, to fried rice, all for under GBP 8. While you're there, you might as well pick up a salad and a dessert to complete the meal.
If you come across any of the aforementioned locations, go in and look around. As an American, I was surprised by the number of healthy "TV dinners."
I found Tesco to be slightly cheaper than the rest and also an excellent place to pick up Twinings Tea (£0.60 for a box of 24 tea bags). Incidentally, this is cheaper than the Twinings Museum/store charges.