Hi having been to London several times there are many different grocery shops, cafes & restaurants that cater for every imaginable culture. Just ask the local people what you'd like to eat or buy & they'll tell you.

Your question is almost impossible to answer - London is one of the world's most cosmopolitan places and you can buy every type of food imaginable. It will depend on who you are staying with and whether you eat at their home or in cafes or restaurants or hotels. As long as you are not too fussy, one thing you can be sure of - you will not be hungry. We do not live on turnips, potatoes, brussels sprouts and sugarbeet ( at least I hope no-one does!)