Eating out
Chinatown and places around Leicester Square have restaurants with touts outside. They can be very pushy, the restaurant expensive and not great quality food. Avoid.
Don’t spend your time just eating McDonald’s or packet sandwiches. You can do that any time (and it’s not healthy). There are local chains that are not much better and are not good value.
Some places do cheaper meals at off peak times of the day eg late afternoon. Some restaurants offer all-you-can eat buffets (but look at the restrictions, and drinks will be extra). If you are in a hotel and breakfast is included, then have a good, healthy breakfast.